In reply to Welly Matt: Another knot used is the figure of eight tied as one knot on both strands at the end of the rope sling. This is poked into a crack using a wooden or plastic poker, which is usually suspended on elastic, from the back of the harness.
If this fig 8 is loaded it tries to spread out into an L shape i.e. expanding in the crack.
I have done a test fall of approximately three metres, fall factor 2, on a loose top rope onto a fig 8 tied in 11mm dynaimc rope. It didn't budge at all.
Don't leave any gear visible in the car if you cross to the Czech side of the border. There is a problem with Gypsies breaking in and emptying the car. It happend to me a few years ago.
Andy