Tony Williams wrote:

I've got a pair of tinsnips, but have never really
got on with them, except for short cuts. On long
cuts, (a foot or so), the parted metal seems to get
in the way of the handles. Must be some trick I'm
missing.

The main trick is to part the metal vertically, so that one side is a
couple of inches higher than the cut, and the other a couple of inches
lower. Gives your and and the snips plenty of room.

--
Grunff