Slide the toolbox drawer all the way out. Look along the sides of the drawer where the glides are touching the toolbox. You should see a small tab of metal or plastic touching each of the glides to the toolbox. These pieces stop the drawer from falling out of the toolbox if it is pulled too far out.
Press both tabs in with your fingers. Pressing the tabs in disables them, allowing the drawer to come out of the toolbox. Pull the drawer straight out to remove it from the toolbox.
Remove the screws holding the glide to the side of the drawer.
Attach the replacement glide to the drawer using the same mounting holes as the original glide. The left and right side glides are mirror images of each other. Make sure you use the glide that is oriented in the same way as the glide you just removed.
Attach the second replacement glide to the other side of the drawer using the same method you used for the first glide.
Push the drawer back into the toolbox. You do not need to press down the tabs to insert the drawer back into place. The tabs only prevent the drawer from being pulled all the way out.