So, once you’ve got those handy, let’s get started.
First up, extend the grainline up to the waistline. This is represented by the blue line on the above diagram.
Draw a horizontal line across the front leg, from the crotch to the side seam, perpendicular to the grainline. The line should be roughly where the fullest part of your tummy will be. If you're not sure where the fullest part of your stomach will be, stand in front of a mirror and hold the paper pattern piece up against you. I've shown this here as a pink line in the diagram.
Draw a vertical line connecting the waistline and the horizontal line you just drew. In this example, I'm going to use the extended grainline.
Finally, draw a line connecting the point where the horizontal and vertical lines you've drawn intersect, with the top corner where the side seam and waistline seam meet. Mark the seam allowance point at the corner. These are the green and orange lines above.
Next, grab your scissors and let's get snipping.
Starting at the crotch, cut the horizontal line and stop where it meets the vertical line. Pivot the scissors and cut up the diagonal line, stopping at the seam allowance marking. From the outside edge, snip from the top corner, stopping a smidge (i.e. a few mm or 1/16 inch) before the seam allowance line.
From the waistline cut down the vertical line and stop just before the cut lines.
You will see you've just made two hinges. We can move these to add length and width where it's needed. Pretty cool, right?
Grab your bit of paper and carefully place your pattern piece on top of it. Stick the lower part of the pattern piece down to the paper to secure it.
Lift and spread the top of the front leg until you've added the desired width and length to the tummy area. Remember that this represents half the pattern piece, so if you add 15mm width, it will add 30mm across the whole front. When you're happy with the amount of space you've added width- and length-wise, stick it down.
Let's tidy up the seams and draw a new crotch curve. I've shown all of this with dark blue lines.
Draw a smooth, curved line connecting the new and old crotch positions. You'll see the front crotch is now more curved and longer.
Smooth out the waistline, drawing a new line to connect the gap in the waistline. You'll also see the waistline is more curved than it once was.
If your pattern has an elastic waistline channel, like the
Esti shorts or trousers, or Safiya from
Make It Simple, square the corner off where the waistline and side seam meet so it can fold back on itself easily.
Finally we need to redraw the grainline, as it will have gone off-kilter at the top of the leg. Using the grainline on the bottom part of the leg as a guide, continue the line towards the waistline. This is your new grainline.
And that's it! I hope you've found this tutorial useful. A little goes a long way here, so if you're unsure where to begin, try adding 15mm (5/8in) width to see how it feels, and assess if you'd want to add any more next time.
