The Spinlock S Cutter is an extra safety feature for when you are using safety lines. It is there for when in an emergency safety lines become unreleasable under high tension. The S Cutter comes in a simple pouch which is easily attached to your lifejacket. If you own the Spinlock Deckvest then it can be stowed in a special pocket made for the S Cutter. It has a guarded razor edge blade that will easily sever safety lines under load.