Built in 1975, the Division Four unit is, like Henry Horner, made of cinder block, which jail authorities quickly learned did not provide the best of security. Because prisoners scraped through the mortar with metal spoons, the jail switched to plastic utensils in 1979. And after several inmates used the top of their dressers to beat through the walls, some in as little time as a minute and a half, the dressers were finally removed in 1981.