Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Drafting basic trouser blocks
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Drafting basic trouser blocks
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Garment Making
Class: Senior Secondary 3
Term: 2nd Term
Week: 1
Theme: Pattern Drafting 2
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Students should beable to out line the bodymeasurementsnecessary for drafting Trouser blocks. draft the Trouserblocks.
below the knee often aligns with the front side seam.
6. Adjust Leg Widths: On the hemline and knee line, extend the width of the front block by 1 cm to 2 cm at each side seam (outside leg). The inseam side often remains the same or slightly wider by 0.5 cm. This provides extra ease for the back. Connect the new knee and hem points to the adjusted side and inseams.
7. Back Waist Darts: On the new back waistline (A'H'), measure from H' inwards by about 4 cm and mark the position for the first dart. Make the dart 3 cm wide and 12-14 cm long. Often a second, smaller dart is placed closer to the centre back, or the back dart is centred about 1/3 of the way from the side seam to the CB.
8. Final Touches: Ensure all lines are smooth. Add seam allowances.
Label: Back Trouser Block, Grainline, CB, Waist, Hip, Crotch, Knee, Hem.
Practical Considerations: Always use sharp pencils and clear markings. Measure twice, mark once. Use transparent rulers for accuracy. The diagrams should be proportionate and clear. For actual classroom demonstration, using a large brown paper roll or a white board is ideal.
A. Definition of a Trouser Block: A trouser block (or sloper/basic pattern) is a foundational, fitted, non-stylized pattern used as a base from which various trouser styles can be designed. It represents the accurate dimensions and shape of a person's lower body, providing a perfect fit without any design ease beyond the necessary wearing ease. It comprises a front block and a back block, which are drafted separately but work together to form the complete garment.
B. Importance of Accurate Body Measurements: Accurate body measurements are paramount for drafting a well-fitting trouser block. Errors in measurement will inevitably lead to ill-fitting garments, requiring costly and time-consuming alterations. The measurements must be taken correctly, with the tape measure held firmly but not tightly, and the subject standing naturally.
C. Body Measurements Necessary for Drafting Trouser Blocks:
1. Waist Circumference: Measure around the natural waistline, usually the narrowest part of the torso.
2. Hip Circumference: Measure around the fullest part of the hips, ensuring the tape measure is parallel to the floor.
3. Thigh Circumference: Measure around the fullest part of one thigh, just below the crotch.
4. Knee Circumference: Measure around the knee joint. This can be taken standing or slightly bent.
5. Ankle Circumference (or Trouser Bottom Width): Measure around the ankle at the desired trouser length. For styling, a desired bottom width is often specified.
6. Waist to Hip Depth: Measure vertically from the natural waistline to the fullest part of the hip.
7. Waist to Knee Length: Measure vertically from the natural waistline to the centre of the knee.
8. Waist to Ankle Length (Outseam/Outside Leg): Measure vertically from the natural waistline down the side of the leg to the desired trouser length (e.g., ankle bone or floor).
9. Crotch Depth / Rise: This is a crucial measurement. The subject sits on a flat surface, and the measurement is taken vertically from the natural waistline to the surface of the chair. Alternatively, it can be derived by subtracting the Inseam from the Outseam.
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0. Inseam / Inside Leg Length: Measure from the crotch point down the inside of the leg to the desired trouser length (e.g., ankle bone or floor).
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1. Crotch Length: Measure from the centre front waist, through the crotch, to the centre back waist. This helps verify the crotch depth and extension.
D. Drafting the Basic Trouser Front Block (Step-by-Step Explanation): Materials: Pattern paper (e.g., brown paper or oza paper), pencil, ruler (L-square or metre rule), tape measure, French curve, hip curve, scissors. Key Calculations (using example measurements for Mrs.
Chioma): Waist Circumference = 72 cm Hip Circumference = 100 cm Thigh Circumference = 60 cm Waist to Hip Depth = 20 cm Outseam (Waist to Ankle) = 100 cm Inseam = 75 cm Crotch Depth = Outseam - Inseam = 100 - 75 = 25 cm Trouser Bottom Width (desired) = 40 cm (divide by 2 for block = 20 cm)
Derived Measurements for Drafting: 1/4 Hip = 100 / 4 = 25 cm 1/2 Thigh = 60 / 2 = 30 cm 1/4 Waist = 72 / 4 = 18 cm Crotch Extension (Front) = 1/20 Hip + 1 cm (or 2-3 cm for comfort) = 100/20 + 1 = 5 + 1 = 6 cm Drafting Steps:
1. Establish Reference Lines: Draw a vertical line down the centre of the paper – this is the Grainline / Centre Front line (CF). Mark the top as point A. From point A, measure down the Outseam length (100 cm) and mark point B. This is the Hemline. From point A, measure down the Crotch Depth (25 cm) and mark point C. This is the Crotch Line. From point A, measure down the Waist to Hip Depth (20 cm) and mark point D. This is the Hip Line. Square lines horizontally from points A, D, C, and
B. Extend them sufficiently to the right.
2. Define Widths on Crotch Line: From point C, measure out to the right 1/4 Hip measurement + 1 cm ease length (100 cm) and mark point B. This is the Hemline. From point A, measure down the Crotch Depth (25 cm) and mark point C. This is the Crotch Line. From point A, measure down the Waist to Hip Depth (20 cm) and mark point D. This is the Hip Line. Square lines horizontally from points A, D, C, and
B. Extend them sufficiently to the right.
2. Define Widths on Crotch Line: From point C, measure out to the right 1/4 Hip measurement + 1 cm ease (25 cm + 1 cm = 26 cm) and mark point E. This establishes the side seam at the crotch line. From point C, measure out to the right the Front Crotch Extension (6 cm) and mark point F.
3. Draw the Crotch Curve: From point F, measure up 2.5 cm and mark point G. Use a French curve or hip curve to draw a smooth curve from a point on the hip line (see step 4) through point G to point C.
4. Define Waist and Side Seam: From point A, measure out to the right 1/4 Waist measurement + 2.5 cm for dart (18 cm + 2.5 cm = 20.5 cm) and mark point H. Draw a straight line from point H to a point on the hip line, 0.5 cm from the waist to hip depth line. This slightly slopes the side seam. Use a hip curve to connect this point smoothly to point E on the crotch line. The ideal connection for the side seam from H to E should curve slightly outwards at the hip, then gently inwards to
E. Front Waist Dart: On the waistline (AH), find the midpoint of (AH) minus 1cm (i.e. (20.5/2)-1 = approx 9.25cm from A) and mark a point. From this point, measure 1.25 cm to the left and 1.25 cm to the right (total 2.5 cm dart width). Draw a dart leg from each of these points to a common point 10-12 cm down from the waistline (dart length).
5. Establish Grainline / Crease Line: Find the midpoint between C and F (i.e., (26 cm + 6 cm)/2 = 16 cm from C; OR (CE + CF)/2 from C, ensuring E is the side seam point). This is more accurately determined by dividing the distance from the side seam (E) to the crotch extension (F) by 2 and measuring from E inwards. Or, find midpoint of CE and from that point measure inwards by (CF-CE)/2 + CF/
4. Let's use a simpler method: find midpoint of the thigh at the crotch line.
Easier Grainline Method: Measure from A out 1/2 of (Hip / 4 + Crotch Extension) = 1/2 of (25 + 6) = 15.5 cm. Draw a vertical line from this point, parallel to CF, down to the hemline. This is the Grainline / Crease Line. Mark this line. All knee and hem widths will be measured symmetrically from this line.
6. Define Knee and Hem Widths: From the Waist to Knee Length (Waist to Ankle minus Inseam (factor for knee position, usually 1/2 Inseam + 5cm) = 100 - (75/2+5) approx 100 - 42.5 = 57.5cm) from A, mark the Knee Line. Square across. On the Hemline (from point B), measure half of the desired trouser bottom width (20 cm) to the left and 20 cm to the right of the Grainline. Mark these points. On the Knee Line, measure half of the desired knee width (e.g., 1/2 Thigh - 5cm, so 30-5=25cm, so 12.5cm each side of grainline) to the left and right of the Grainline. Mark these points.
7. Draw Leg Seams:** Use a ruler to connect the side seam point E (on crotch line) to the knee line point and then to the hemline point, forming the side seam of the leg. Use a slightly curved ruler or hip curve to connect the crotch point (C, curving through G) to the knee line point and then to the hemline point, forming the inseam. The inseam should have a slight curve, so 12.5cm each side of grainline) to the left and right of the Grainline. Mark these points.
7. Draw Leg Seams: Use a ruler to connect the side seam point E (on crotch line) to the knee line point and then to the hemline point, forming the side seam of the leg. Use a slightly curved ruler or hip curve to connect the crotch point (C, curving through G) to the knee line point and then to the hemline point, forming the inseam. The inseam should have a slight curve, particularly from the crotch to the thigh.
8. Final Touches: Add seam allowances (typically 1.5 cm) if drafting a pattern for cutting.
Label all sections: Front Trouser Block, Grainline, CF, CB (if back), Waist, Hip, Crotch, Knee, Hem.
E. Drafting the Basic Trouser Back Block (Step-by-Step Explanation): The back block is drafted using the front block as a guide and adjusting for the fuller back hip and seat area. Key Calculations (using Mrs.
Chioma's example): Back Crotch Extension = 1/8 Hip + 0.5 cm (or 1/10 Hip to 1/8 Hip) = 100/8 + 0.5 = 12.5 + 0.5 = 13 cm Back Waist Dart = 3 cm (can vary based on waist/hip difference) Back Waist Rise = 2-3 cm (back waist is usually higher than front) Back Outseam is generally the same as front. Drafting Steps (Using the Front Block as a Base):
1. Trace Front Block: Place a new sheet of pattern paper over the drafted front block.
Trace all key lines of the front block: side seam, inseam, hemline, crotch line, hip line, and grainline. Remove the front block. Label the traced lines as your construction lines for the back.
2. Adjust Back Crotch Extension: Extend the crotch line to the right from the front block's crotch point (let's call it C') by the Back Crotch Extension (13 cm). Mark this new point as F'.
3. Adjust Back Waist Rise: Extend the Centre Back (CB) line (the CF line of the front block becomes CB for the back) upwards from the front block's waistline by 2.5 cm to 3.5 cm (for the higher back waist). Mark this new top point as A'. From A', measure out horizontally to the right 1/4 Waist + Back Dart (3 cm) + ease (1 cm) (18 + 3 + 1 = 22 cm) and mark H'. This is your new back waist point.
4. Draw Back Crotch Curve: From the previous front crotch curve (let's say it met the crotch line at point X), measure diagonally from point X towards F' by about 2 cm and mark a guide point. Use a hip curve to connect the new waist point H' to the hip line, then smoothly through the guide point on the crotch line, and finally curving out strongly through F' and blending into the front inseam (traced inseam line) at about the mid-thigh level. This is a crucial and often complex curve, requiring careful handling of the hip curve.
5. Adjust Side Seam: The side seam of the back block will generally extend slightly outwards from the front block's side seam. From the hip line point of the front block's side seam (E'), measure out 1.5 cm to 2 cm and mark a new point. Connect the new back waist point H' to this new hip point, and then smoothly curve down to meet the front side seam at the knee level. The curve should be gentle to accommodate the back hip. The side seam below the knee often aligns with the front side seam.
6. Adjust Leg Widths: On the hemline and knee line, extend the width of the front block by 1 cm to 2 cm at each side seam (outside leg). The inseam side often remains the same or slightly wider by 0.5 cm. This provides extra ease for the back. Connect the new knee and hem points to the adjusted side and inseams.
7. Back Waist Darts: On the new back waistline (A'H'), measure from H' inwards by about 4
Custom Tailoring Business (Entrepreneurship): Students who master trouser block drafting can open or work in tailoring shops, specializing in custom-made trousers for individuals. This is a highly sought-after skill in Nigeria, enabling them to create well-fitting trousers for various body types and preferences (e.g., traditional attire, corporate wear, casual trousers), providing a direct livelihood. Ready-to-Wear Fashion Production (Industrial Garment Making): The ability to draft accurate blocks is the foundation of pattern making in industrial garment factories. Students can pursue careers as pattern makers, translating design sketches into production-ready patterns for large-scale manufacturing of trousers for local and export markets. This skill is critical for ensuring consistency and fit across different sizes in ready-to-wear lines.
Costume Design for Arts and Culture: In the vibrant Nigerian entertainment industry (Nollywood, theatre, traditional dance groups), costume designers frequently need to create custom trousers for performers. Drafting skills allow them to produce historical, cultural, or contemporary trouser styles that fit performers perfectly, enhancing the authenticity and visual appeal of productions.