When the piston rod is fully out or fully in, and the connecting rod and the crank in consequence lie in a straight line, the crank is said to be at a dead point or dead center. When the crank is in this position the admission of steam will not produce motion since the thrust would be absorbed by the bearings. A locomotive engine must be constructed so that it may be started in any position. In order that this may be done the engine must have at least two cylinders, and the cranks must be set at an angle to one another, so that when the crank of one is at a dead point the other has reached a position where it exerts its maximum turning power.