Abstract: A magnetically anchored quick release pin is provided for quickly and accurately preventing movement between two objects and/or quickly changing the relative position between two objects. One such use is in a weight lifting machine providing for variable resistance, which can be adjusted manually during a workout routine. The weight lifting machine includes one or more guides and a stack of weights which are slidably mounted on the guides and movable along the guides from a rest position to an elevated position. The weight lifting machine also includes a selector member and a lift member. Each of the weights includes an opening to receive a selector pin. The openings are aligned to define a passage through the stack of weights to allow the selector pin to couple each of the weights in the stack to the selector member.