The present invention concerns an apparatus for coupling a beam 120 to a track 500 along which the apparatus can move, comprising an arm assembly 102 having a first end arranged to interface with the beam 120, and a second end opposite the first end. The apparatus also comprises a head assembly 104 coupled to the second end of the arm and arranged to engage with the track 500 to inhibit movement of the head assembly along the track, wherein the head assembly 104 comprises a receiving portion 110 and a plastics material 112 received within the receiving portion 110, such that the plastics material 112 provides a contact surface between the head assembly 104 and the track 500 when the head assembly 104 is engaged with the track 500.