Cylinder straps (aka stage straps) provide an efficient means of using bolt snaps to attach the cylinder to your harness hard points (D-rings or sidemount rails). In some designs the strap may also be used to help carry the cylinder. The strap itself is a piece of round cord or flat webbing that creates secure attachment points for two stainless steel bolt snaps. The strap encircles the cylinder's neck and is secured at the cylinder's base by a stainless steel hose clamp. A fabric sheath on the clamp is used to prevent the clamp from causing damage to the cylinder or abrasion against the diver. Elastic hose retainers are used to dress the regulator hose neatly against the cylinder.
Metal to metal stage rigging, brass alloy, and boat style snaps are no longer considered best practice among experienced divers. Even the best snaps can jam, but brass snaps are prone to jamming if not carefully maintained and they'll cut your thumb too. The boat snap (aka "suicide clip") is very effective as a line trap, and notoriously ineffective as a reliable attachment device. It's also proven to be a bad idea to clip yourself to bottles that have the clips permanently attached to the tank using metal-to-metal rings or clamps. Should a jam or entanglement occur, a diver might find it impossible to free themselves from the bottle. Straps and stainless steel marine-grade snaps that can be cut free in case of entanglement are now the accepted form of stage bottle rigging.