In reply to mattrm:
> Normal sized prussik has always served me well. Also you can wrap the sling around your foot a few times to stop it slipping off.
Or you can wrap the rope around you foot a couple of times instead of using a Prussik if you only have one or jus want to quickly gain a few meters.
OP: You can always extend them with cord or slings. Better that you're able to improvise with what you have than that you have 'perfect' kit.
jk