Tips & tricks

Setting snaps: top, bottom and what to do if it won't hold

Which part goes on top, which underneath, and why won't the snap hold? How to set plastic and metal snaps that stay put, and how to rescue the ones that don't.

Cross-section of a closed flap: on top the cap outside and the socket with its opening facing down, below on the under-layer the stud with its knob facing up and the cap on the inside.

Snaps are quick to set and last a long time if two things are right: each part sits on the right layer, and the fabric underneath is firm enough. The Kirsche wallet, for example, closes with snaps.

Most problems happen in the seconds before pressing. A swapped part, a post that's too short or a single thin layer of fabric, and the snap falls off after a few days. Here's how to avoid that, and what to do if it happens anyway.

What you need

Plastic or metal snaps, a few more than you need
Matching pliers or press
Awl
Chalk or a disappearing marker
A pin
Firm fusible interfacing or a scrap of felt for reinforcing
Fabric scraps for testing
Side cutters (only for removing)

Step 1

Know the parts

Side view of the snap parts: on the left in plastic a cap with post, socket, stud and second cap, on the right in metal a cap with hollow rivet, socket, stud and back.

A snap has two halves, and each half has two parts:

The socket is the female part with the opening. It comes with a cap that is pressed against it from the other side of the fabric.
The stud is the male part with the knob. It also gets a cap, or with metal snaps often a flat back.

With plastic snaps the cap has a post that goes through the fabric and is flattened when you press. With metal snaps there is a hollow rivet on the cap or back that is flared when you set it.

Sort the parts into two little piles before you start: cap with socket, cap or back with stud. That way you won't grab the wrong one.

Step 2

Which part goes where: socket on top, stud underneath

The rule of thumb: the socket goes on the piece that lies on top when closed, usually the flap. Its cap sits on the outside and is the nice side you see. The socket itself sits on the inside of the flap, with the opening facing down.

The stud goes on the under-layer, on its outside, with the knob facing up. Its cap sits on the inside and won't be seen later.

Before you press, do the mirror check: push the parts loosely through the holes without pressing, and close the flap. If opening and knob meet, it's right.

Step 3

Mark the position on both layers

On the left a closed flap from above with a pin through all layers, a chalk cross and an arrow showing the distance to the edge. On the right the same piece opened, with chalk crosses on the flap and on the under-layer lined up exactly.

Close the piece the way it will be used later and push a pin straight down through all layers at the spot you want. Mark the pin hole on top and underneath with chalk. Then open it and check that both marks line up exactly when you close it again.

The centre of the snap sits at least 1 cm from the edge, a bit more for large snaps. Otherwise the cap sticks out over the edge or sits on a bulky seam.
If your pattern has a mark, transfer it while cutting, see Cutting is half the sewing.

Not sure? Fold a paper version first, poke through both layers and check that the holes end up where you want them when it's closed.

Step 4

Reinforce: never into a single thin layer

On the left, wrong: a single thin layer of fabric has torn, cap and socket are coming loose. On the right, correct: several layers with a piece of felt behind, the snap sits firmly, next to it an awl makes a small hole.

A snap only holds as well as the fabric it sits in. Every time you open it you pull on that little hole. In a single thin layer it will tear out sooner or later.

Plan for at least 3–4 layers of fabric at that spot, for example outer fabric, lining and interfacing.
If that's not enough, fuse a small piece of firm interfacing behind it or put a scrap of felt between the layers. Which interfacing to use is explained in Fusible interfacing: which one for what?.
Make the hole with an awl. It pushes the threads apart instead of cutting them. Make it just big enough for the post to go through. A punched or cut hole quickly ends up too big.

Step 5

Setting: press straight and check by turning

Snap pliers from the side: the upper and lower dies press cap and socket together straight through the fabric layers, arrows squeeze the handles together.

Push the cap through the hole from the outside and put the matching part on the post. Before you press, look at the post: it should stick out about 2–3 mm above the fabric. If it's shorter, it can't be flattened properly. If it's much longer, it bends sideways.

Place the snap exactly in the centre of the pliers or press and squeeze straight and evenly, not at an angle. With plastic snaps, firm pressure until the post is flat is enough. More force doesn't make it last longer.

Then the test: hold the snap and try to turn and wiggle it. It must not spin loosely. If it does, read on in the next step.

Step 6

If it won't hold: find and fix the problem

Three panels: with thick layers a short post doesn't reach the socket (wrong), a longer post reaches into it (right), and side cutters cut off a cap, with the new position 5 mm away shown dashed below.

It falls out: the post was too short for the thickness, or the layers are too thin. Reinforce the spot and use snaps with a longer post for thick layers.
It won't close: the parts are swapped, for example two sockets facing each other, or they're not lined up.
The plastic has cracked: too much pressure. Next time, only press until the post is flat.

You can remove a wrongly set snap: carefully cut through the cap with side cutters and pull out the pieces. Watch out for the fabric while you do it. The old hole is usually stretched afterwards. Place the new snap about 5 mm away or on a reinforced spot.