This hiding spot is in the room across from the red lift.

Go in there and you should see a basketball net hanging up on the wall with a shelf or something beside it to the left. Jump on top of the shelf thing and then crouch jump to the basketball net.

You should end up crouching on the rim. Just wait for someone to come in the room and then tale them out! Is great for playing team swat because they always seem to run right past the room so you can just pick them off as they go along.