Page "Fielding (cricket)" Paragraph 67

Another attacking placement on the leg side is the leg side trap, which involves placing fielders near the boundary at deep square and backward square leg and bowling bouncers to try to induce the batsman to hook the ball into the air.

For slower bowlers, the leg trap fieldsmen tend to be placed within 10 – 15 m from the bat behind square, to catch leg glances and sweeps.