 When both handrims are grasped together, the chair may be propelled forward or backward in a straight line.When either handrim is moved independently, only a single wheel is used and the chair will turn left or right in response to the handrim used.Some wheelchairs, designed for use by hemiplegics, provide a similar function by linking both wheels rigidly together and using one of the footplates to control steering via a linkage to the front caster.