When nothing else is available, a few carabiners or figure eights and webbing may be used as emergency ascenders. These are advanced configurations only to be used by competent people that have practiced with them beforehand.
A Bachmann Hitch uses a carabiner and a rope/webbing tether configured with a Klemheist knot. It can be moved up the rope similarly to a handle ascender, but weight may only be applied to the loop at the bottom (not the carabiner). Applying weight to the carabiner will tend to slide the hitch down the rope.
The croll can be replaced by couple carabiners in a Lorenzi configuration or a Figure 8 in Italian mode