Sometimes people need something a little fancy for their lawn fence line or maybe a shed. Really, there are all sorts of uses fit for self closing door hinges. They are like regular hinges that can screw onto a wood surface. They hold wooden doors and can hold somewhat heavier doors if a third or fourth hinge are used. What they are really great for is just gently swinging a door back in place once it is open. It is great for pets or for people who sometimes forget to close the shed door.
As the hinges are opened, some tension rises in the springs. This tension is stored energy that guides the door back to its closed position. This works great with a bolt mechanism that gives to slight pressure and then holds the gate in place. Getting it to work means knowing the force that a gate lock will accept, so buying the right spring-loaded hinge is one reason to visit a website.