Ultimate Trousers Sewalong No. 6: Inserting the Zip

The Ultimate Trousers have an invisible zip in the side seam, which when done up should - as the name suggests - be completely invisible. We're going to have a go at inserting it as flawlessly as possible.

For this stage you will need an invisible zip foot and a standard zip foot. The ones for our machine  (Janome CXL301) look like this...



We will be using the invisible zip foot to attach the zip to the trousers, and then the regular zip foot to close up the gap left at the bottom between the zip and the existing side seam stitching.

Firstly, for those of you who are taking in your side seams at the top, as discussed in our fitting post, we're going to show you how to find the correct placement for your zip based on the markings you made.

We attach invisible zips onto the right side of our trousers, which means in order to get the zip in the right place, you somehow need to transfer your markings from the wrong side of the fabric to the right side. Of course, however, you don't want to actually mark the right side of your fabric, so we're going to show you how to do this with pins.

Lie your trousers down inside out, with your new side seam line markings facing up. Place a couple of pins all the way through the trousers.


Carefully lift up the top layer of fabric without pulling out the pins. On the right side of the bottom layer of fabric, place new pins in where the existing ones pierce the fabric, as shown below.



You can now pull the layer apart, and on both the front and back of the trousers, you now have pin markers showing you where you need to line up your zip teeth.

Place your zip on your trousers with right sides together. Line up the zip teeth with the very edge of the pins you have just put in. Pin the zip in place.


Of course, if you don't need to bring the side seams in at all you can skip this step. Just make sure you line up the zip teeth with your 1.5cm seam allowance instead.

And remember, the start of the zip teeth need to be 1.5cm from the top of your trousers.

Attach your invisible zip foot to your sewing machine, and starting at the top of the zip, sew down to the zip pull. Don't forget to backstitch at the beginning and end.


As you sew you might like to uncurl the teeth slightly with your fingers, allowing your line of stitching to get as close into the teeth as possible.

When you get to the zip pull you won't be able to go any further as your invisible zip foot will get in the way. This means you will now have an unstitched section of your side seam in beween the zip and your first line of stitching. In order to close this up, we're going to use a standard zip foot.


With the hem of the trousers closest to you, sew the little gap shut with your standard zip foot. This will allow you to get up close to the line of stitching and sew the gap closed as neatly as possible. Hold the zip tape out of the way as you sew this section - you don't want to get it caught up here.

Repeat this process for the other side of the zip, making sure that when you pin it in place it is not twisted in any way.


Once you have done that you will have a perfectly inserted zip that appears invisible from the outside when done up.


If you have any problems inserting your zip do let us know.
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