Gas welder fittings connect gas lines and hoses on your welder. The sole purpose of some of them is to keep you safe. For example, quick disconnect fittings for torches and regulators provide automatic shut-off, and flow check valves close instantly for complete shut-off if in case of a reverse flow of gas. Flashback arrestors provide a double layer of protection with a built-in flow check valve to further prevent reverse flow. Brass lugs, terminals and other welding cable connectors are covered with a rubber boot to insulate the connector and guard against electrical shock.