What is LATCH and what are the weight limits for using it?

LATCH (Lower Anchors and Tethers for CHildren) is a system of fixed lower anchor bars and a top tether anchor built into vehicles made after September 1, 2002, that allows you to attach the child restraint without using vehicle seat belts. Do not use the lower anchors when restraining a child weighing more than 24.9 kg (55 lbs).