
Today, we are inserting the zipper into our pants and making the fanciest of flys – with a facing and a fly extension! FANCY Y’ALL. This is my personal favorite part of the pants-process – when they actually turn into pants, and not just 4 giant pieces of fabric flapping around the sewing room
We will be sewing steps 9-13. I know it sounds like a lot of ground to cover, but this should actually go a bit faster than the welt pockets – plus, you only have to sew one zipper, not two!
Here is your background music for this task. It seems fitting, although I’m guessing Danzig’s fly isn’t exactly the same fly we are dealing with today ![]()
Steps 7-8 should already be completed at this point, FYI!

Take your interfaced fly facing (piece 11) and finish the curved edge.
Sidenote: The pattern placement wasn’t intentional when I cut this piece out, but HAHAHAHA dude is totally going to be lurking the inside of my pants!

Sew the facing to the right front, right sides together, stopping at the notch.

Trim & grade the seam allowances, understitch, and press the facing to the wrong side.

Get your fly extension (piece 10) and fold in half along the fold line, right sides together, and sew along the bottom. Trim seam allowances, turn right side out and press. Sew and finish the long side.

Place your zipper over the long finished edge of the fly extension, face up, with the zipper stop matching the notch. Sew. If your zipper is longer than 4″ (and really – where the hell does one find a 4″ zipper?), go ahead and match up the end with the notch and let the zipper excess hang off the top. We’ll cut it off when we get to the waistband attachment.
Sorry that the left side of my zipper tape looks all chewed up, it is. We got in a fight.

Sew the zipper to the left pants front, face down, stopping at the notch. You can sew directly over your previous stitching line, to make things a little easier!

Turn the facing to the back and edgestitch close to the zipper teeth.

Now this might be a little hard to see, so bear with me here! Zip the whole thing closed, and then pull your right front over to the left from until the fly facing seamline is matched up with the second notch on the left front. At this point, I like to pin the whole thing closed so it doesn’t try to get sneaky when I push everything under the sewing machine.

Flip your pants over; the right (un-attached) side of the zipper should be lined up with the fly facing. Pin the two of them together as shown, being careful not to catch anything else in your pins – no pants front, no fly extension. Just the facing and the zipper tape! As you can see, the zipper tape won’t go all the way to the edge – that’s ok! It’ll end up somewhere in the middle.
Go ahead and sew the zipper tape to the fly facing, using two lines of stitching.

Flip the pants back over – it’s time to draw the stitching line for your fly! Yeeeeahh!!
Keeping the pants pinned close, locate the zipper stop and mark it (I used a pin, but you can also use chalk or whatev). This isn’t totally necessary, but you do want to be careful that you don’t try to sew through the stop – it could break a needle (“Wah” you say) or throw off the timing of your machine (“FUCK” you say). So watch out!

I like to start at the top and work my way down when marking my fly line (I know Tasia’s is the opposite, so do whatever you want, yo!). Measure 1.5″ from the center in a straight line, curving the line as you reach your marking for the zipper stop. Bring the line under the zipper stop to ensure that you don’t sew over it.

Here is my fly all marked up.
Don’t you love my BRIGHT ASS NEON YELLOW marking!? Liz sent me a couple pieces of this marking wax and a brand new box of hook&eyes, after I lameted about accidentally throwing mine away right after I bought them in Chicago. It was completely unexpected and totally amazing of her to do, but what else do you expect from someone who brings macarons to a sewing meet-up?
Thank you again, Liz!
ANYWAY, topstitch right over your markings, directly through the pants front and fly facing. Leave the fly extension out of this – you do want the zipper to actually work, no?

Since the poor extension feels lonely, give her a couple of tacks to the facing so they can still hang out. You can do this by hand, or the lazy way like me – with a tiny zigzag on your machine
This picture was surprisingly hard to take; look at the diagram in the instructions if you need more elaboration on where to stitch.

And that’s it! You should have a beautiful fly zipper, with a gorgeous fly facing and an outstanding fly extension.

Doesn’t that look professional as fuck?
Go ahead and sew up your side seams as indicated in step 14. We only have a few more steps left!






































