THE BLOCK is a security system that prevents potential thieves from breaking in by lifting the sliding door out of its track. This is a common method of breaking into houses or apartments that is so easy, even the wild Chacma baboon troops in the Western Cape have learned this technique of breaking into houses! THE BLOCK is made from high-security steel with a rust-proof all-weather coating - it is permanently and securely fitted to the floor or deck on the outside of the sliding door track, out of the way of foot traffic. Unlike track bolt type locks which you have to remember to lock to be effective, THE BLOCK is permanently in position protecting you and your family.