How to sew a zipper fly for your pants

The zipper fly is an element that we will have to sew many times throughout our sewing life. It is a type of closure widely used in pants and even in some skirts.
What we have to be clear before we start is that when we sew a fly we will have 4 main pieces: the two front pieces of the pants and the two crossing placket pieces of the fly.

If the crossing pieces are separate from the pants as in this case I am going to explain, the pattern of the front does not change from left to right side.

**If the upper crossing is part of the front pant pattern simply skip the step of joining this part.

So we have the front pants ones, the lower crossing and the upper crossing. Let’s say our fly is 20 cm long. The crosses will have a length of 20-22 cm and a width of 4 cm as a standard measure although this varies depending on the design. On the other hand we will have our fronts with an obligatory notch at 20 cm from the waist to mark the position of the fly. I for my part always mark another 2 cm above the previous one.

It is normal to work in this case with a 18-20 cm zipper, but if you use a longer one, all you have to do is cut them at the end.

Important
The seam allowance on the fly seam must be 1,5 or 2 cm.

This piece you see here is the lower cross. In the first picture you can see it already folded in half to a width of 4 cm but in reality the original piece should be twice as wide, that is, 8 cm and should be folded.
We leave this piece ready since we are going to start assembling the lower side.

Place the zipper right sides together with the pants at a distance of 0.5 cm from the edge.
Then we place the cross placket on top so that the zipper is in the middle of the cross placket and the pants.

Stitch by the seam allowance until you reach the end of the zipper, the first notch.
Turn and press. Notice that the zipper teeth are slightly separated from the seam.

Let’s see the other side. You should place the piece right sides together and pass a runningstitch to the seam allowance of the edge until we reach the notch. Turn and press.

**If the upper crossing is part of the front pant pattern simply skip the step of joining this part and just press the cross to the inner.

Optional – Stitch close to the seam on both sides up to the end of the zipper.

Now have the legs (crotch seam) already assembled and join the center seam starting from the back until you reach the end of the fly.

With the fly in front of you, make sure that the position fits well and stitch along the edge of the mounting side (felled seam).

It remains to attach the other side of the zipper to the cross placket that mounts. You can fasten it with pins. Please note that the stitching should only be done on the placket piece, it should not be visible on the right side of the pants.

This stitch besides decorating, what it does is to hold the inner placket, so once youhave sewn the zipper we will pass this stitch. Remember to move the cross placket of the other side apart, because if you catch it with the machine you will not be able to open the pants.

Put the lower cross back into position and join it to the upper cross with a small stitch in the lower corner. This is done so that the piece is fixed without dancing around.