They go on the corners of the dash top if you don't have a dash pad.
My car has them with no dash pad.Well, learn something new every day. Both my early A's have the pillar trim - plastic for my Barracuda, chromed metal for my 63 Valiant convertible, so had no idea these pieces were used WITH a dash pad in early A's with no pillar trim.
What about no dash pad? I've always assumed they were the cars that would have used these little end caps, but maybe not?