1.   A wire is stuck up a coin tray to block the beam that counts coins as they are paid out.

2.   Others have tried to slip a wire up the coin tray to block the beam that counts coins as they fall out.

3.   Test the electric eye by blocking the beam between the modules as the door closes.

4.   The films were analyzed in a widely-used procedure in which the density of bones is determined by how well they block X-ray beams.