Tibloc on my harness on Andromeda Strain
I always carry a Tibloc on my harness, along with a couple of prussic's, knife and in winter v-threader (made out of a coat hanger!). Can use for simul-climbing by clipping to a piece of gear with a large diameter locking carabiner with the rope running through the biner. Use two if you are climbing on double ropes. This way if the second falls they fall on the piece of gear and don't pull the leader off! WARNING!!! Cannot give slack to the second with this system, so they better have their poop together!
Photo Copyright: Stephen Koch Collection