There are two ways to do it with the normal RC glow engine. The first is to use a prop where the blades are pitched in the opposite direction (the reverse or left handed prop as Pe said) and the engine runs the normal way. The second way only applies to an engine where the front housing is removeable (and to some rear induction engines) when you turn the front housing 90 degrees anti-clockwise. This allows the engine to run in the reverse direction as well as it would the usual way. With this system you use a normal propellor but put it on the crankshaft backwards.

Correct me if I'm wrong Pe, but I think you were talking about large reed valved ignition engines?