The purpose of this exercise is to isolate the bicep in order to strengthen and gain size in the bicep.
This exercise will be done with a dumbbell, one arm at a time but, choose a lighter weight than you would for a standard dumbbell curl. First, sit on a bench with your legs spread and the dumbbell on the floor between them. Pick up the dumbbell with your right arm and place your upper arm (directly above the elbow) on the thigh of your right leg. Now with your palm facing away from your thigh, curl the weight until your arm until the dumbbell reaches shoulder level. Your upper arm should remain stationary throughout this movement. Contract your bicep hard during the movement, squeeze the bicep at the top of the movement, and then slowly lower the weight under control to the starting position. Repeat this for a set number of repetitions and then complete the same number of repetitions with the opposite arm.
Avoid using momentum throughout this movement, it will be easier to swing the weight up but in order to fully work the bicep the movement need s to be done under control.