There are many different companies that sell corner guards and the price will depend on the type, length and width of corner guard you're buying. 

1. Measure the wall where you will be installing the wall guard to determine the length needed.
   
2. Cut the aluminum retainer to length, keeping in mind that the end caps will extend 1.5″ beyond the aluminum on each end...

A wall guard is a wall protection product designed to protect the length of a wall, such as a hallway or corridor, from damage. Common in hospitals and other healthcare facilities these products are installed at a specific height along the wall to act as a bumper for beds, carts, and other movable objects that can cause costly damage to walls. Wall guards are often complementary to corner guards and handrails in order to protect the entire building. These items are commonly referred to as bumper guards, wall guard, crash rails, or chair rails depending on the manufacturer.