How to Create a Shaft Brake ?

[Geoff H.]

My transmission was just rebuilt (velvet drive on Formosa 51/Ford Lehmnan 120 hp) and my mechanic insists that for world cruising I want to fashion some kind of shaft brake; he suggested a "poor man's approach -- a pipewrench!!) Is there a less "poor" way to go w/o resorting to the complications of hydraulic brake systems?
I like the idea of stopping my prop from turning while sailing, and like idea of something that's not expensive or complicated, and that doesn't add another damned system that needs manintenance. Any thoughts?