Countersunk bolts can be used to secure composite, French, deck, wood, double or other door openings. This great little device features a self-tensioning spring that provides tension in both the retracted and extended positions. The door opens (top to bottom) to provide a safety feature. Our countersunk bolts are machined from solid stainless steel and resist corrosion and rust, making them strong and durable. Installing countersunk bolts can be a great way to improve the security of your home. Reinforced with screws to improve the stability and smoothness of the structure. Installed on non-moving leaves of double door openings. All-in-one switch design, convenient for daily use, say goodbye to pushing and sliding, the comfortable touch and concealed style of this lever will surely bring you a pleasant using experience and match your modern decoration . Easy to install with rust-proof screws and surface strike for installation. Like calm.