Stanford University students have rebuilt a small shantytown symbolic of unity with South African blacks while campus police continue investigating the vandalism that destroyed the original cardboard and plastic shacks. "As far as natural forces are concerned--the wind and rain--we're building it strong enough to withstand that," senior Mario Huerta said. "As far as human forces, I don't know." He said members of Stanford Out of South Africa would sleep in the shantytown to protect it. The original was erected Jan. 20 to show solidarity with the anti-apartheid movement and was found flattened last weekend.