A traction apparatus (1A) includes at least one traction member (51) which engages a surface (10A) against which traction is to be provided. The traction member can move relatively freely in one direction over the surface but has high resistance to movement in the other direction. The apparatus can be made to move by having a number of traction members (51-56) which move or oscillate relative to each other. There are preferably a large number of traction members which are in the forms of bristles in a brushlike part of the apparatus. The apparatus is suitable for use in down-hole tools. The bristles are bent in a first direction by being constrained in a hole facilitating movement in the opposite direction but preventing movement in the first direction.
