Apparently Schaefer Marine no longer makes rope clutches. Now heres the real irony, two of the clutches are all metal. 4 of them only have plastic handles... handles that I feel are about to snap off at every use. The rest of the clutch is all metal.

"The Schaefer 2nd generation Clutch (Halyard or Sheet Stopper, or Line Jammer), known as the EGR (Easy Grip & Release), was introduced in 1983. It featured all aluminum (black anodized) construction, except for S.S. bolts and springs. It was also available in 2 sizes: the smaller handled line 1/4"-3/8", the larger 3/8"-1/2". Both sizes were commonly available as single units, or in banks of two or three. Originally these units had color-coded plastic-tipped handles, but later on the handles were anodized in different colors and had no plastic tips (much less gooey in the hot sun). Although they gripped and released easily, under extreme loads they didn't hold as well as the First generation units. The EGR (Type 2) Clutches were produced from 1983-1993. A limited supply of these items are still available."

http://www.rigrite.com/Hardware/Rope_Clutches/Sch_Stoppers2.html

Apparently I have the EGR type for my large clutches, and the early version of the smaller EGR clutch for my smaller clutches.

They seem to work by operating a cam that pushes a metal plate that pinches the line.