Split the Troop into groups of about 6 or 8 Scouts. Ask the Scouts to stand in a rough circle. Each Scout clasps the hand and wrist of another Scout around the circle and then repeats with the other hand and a different Scout. This should form a knot of arms. The group now have to untie the knot without letting go, by passing under their own arms, under other peoples arms or by turning round under their own arms.