The mast clamp can save you hundreds of dollars in deck repairs if your mast happens to come out of the mast step during a capsize. This stainless steel lock prevent the mast from coming out of its step. This lock has a rubber insert and should be clamped around the mast just under the deck. We suggest you use the mast clamp as well as the mast tie in for double security. The mast lock comes with a line so that it can be attached to the mast step so you don't lose it.