Snaps are used in many webbing assemblies. They provide a simple mechanical connection between two pieces of webbing or webbing and a solid surface. To install snaps on webbing we use a pneumatic press with purpose built dies but you can get "hand drive" tools which only require a mallet.
Snaps have an interesting history. They are measured using a system that predates the metric system. Two sizes of snaps are common, Ligne (pronounced LINE) 24 is used on boat covers, bag closures, leather working and on straps. It is the most common size in our industry. Ligne 20 snaps are sometimes referred to as "baby snaps" and can be found on clothing. To date we have not encountered a Ligne 20 snap on a strap. The two sizes require different die sets and are not interchangeable. Below is a photo with Ligne 24 snap dimensions.
We stock Ligne 24 snaps in both marine grade stainless steel and black oxide coated brass. They can be special ordered in plain brass and nickel plated brass.
Ligne 20 snap cap has a nominal diameter of 0.51"