"The Natural Philosopher" wrote

The Medway Handyman wrote:
Three poles in a triangle, one longer that the other two, used with a
block & tackle attached to the longer one?

Its on the tip of my tongue!

sheerlegs?

Apparently spelt shear legs.
Not quite sure why, when the legs are in compression!
See http://www.hss.com/g/69310/500kg-Shearlegs.html for details.

Phil