In article , Jonathan Cook
wrote:

A good tip for this, when you're out in the field, is to put the rod,
horizontally, behind the backs of your knees (which are together). You
lean down, and grip each half of the rod, each wrist just outside a
knee. Then if you move your knees apart, while still gripping firmly,
you'll find the two halves of the rod being pulled apart in a straight
line - which is difficult to do any other way.

Lazarus