The plaster walls in my 71 yr old home have several hairline full-height cracks in them. When I push on the walls, they move slightly (approx 1/16") but are not in danger of collapsing. I've heard of special screws made for plaster walls that will reinforce the walls to prevent them from moving and initiating the cracks again. Does anyone know the name of the screws and where I can purchase them? Also, how do you properly install them?