There are three kinds, they are fitted differently, and the failure mode is the same for all of them: the fabric behind is not strong enough.
Sew-on snaps. Mark the position of the ball half first and sew it on with four or five stitches through each hole, taking care that nothing shows on the right side. Then rub tailor’s chalk on the ball, press it against the other layer to transfer the mark, and sew the socket half there. Marking by transfer rather than by measurement is what makes them line up.
Hammer-in snaps. Fitted with a die set and a mallet on a hard surface. Punch or cut a hole, insert the prong or post, place the cap, and strike squarely — several firm blows rather than one wild one. An uneven strike deforms the cap.
Pliered snaps, including plastic ones for children’s clothing, use dedicated pliers with matched dies. More controlled and more consistent than a mallet.
Reinforce behind every metal snap. Interfacing at minimum, and a scrap of firm interfacing or a small patch of fabric where the load is real. A snap in a single layer of light fabric will tear out, and it takes a hole with it.
Test on a scrap of the same layers first. Die sets are unforgiving and there is no undoing a fitted snap without damage.
Placement. Mark from the closed garment, not from the pattern, and check the two halves meet with the garment lying as it will be worn.
Questions people actually ask
My snaps keep pulling out.
Not enough fabric behind them. Add interfacing or a reinforcement patch — the snap is only as strong as the layer it is anchored in.
Do I need special pliers?
For hammer-in snaps a die set and a mallet is enough. For plastic snaps the pliers are effectively required and they are far more consistent.
Last reviewed 2026-08-11