Weight Drop TBI models are used to replicating focal cerebral contusions as well as traumatic, diffuse brain injury by axonal damage. Attach a metal loop to the top end of the desired weight allowing the fishing line to be fastened to the weight. The plastic guide tube is held in place with a clamp stand and positioned above the scored tin foil. The fishing line is then attached through the metal loop to the weight ensuring that the bottom of the weight hangs freely over the scored tin foil. The fishing line is then connected to the clamp stand, and the weight is drawn up through the plastic guide tube with the fishing line and secured in its position with an Allen key pin.