A sliding glass door security bar is a simple device which is placed in the track of a sliding glass door to prevent it from opening. This type of security bar can usually be purchased from the door manufacturer, or you can make one from a piece of wood or pipe cut to the right size. Certain designs can be placed at the top of the door (rather than on the floor) to prevent children from opening the door.
When positioned properly, a security bar should stop a door from sliding open at all. In conjunction with the door's lock, the bar will effectively prevent any movement. The right size for a bar of this type should be no more than 1 inch shorter than the length of the track.
Placing a security bar in a higher-up position provides a better level of security. A bar wedged up high like this, however, can be knocked out of position if someone bangs on the door.
If you have a dog, consider that dogs like to pick up sticks. Choose a bar made of heavier metal, or position your wood bar up high out of the dog's reach so he can't dislodge it from its secure position.