You know the problem of sighting steep legs - having to visually extend the sighting line, and to estimate the position by moving the device up and down? Mounting two (plexi)glass bars on the compass (see picture) greatly improves sighting accuracy.
There is a detailled description of the mounting method in Stalactite 41,1,1991.

infos/questions: Rolf Siegenthaler

or

Christian Bieri