Pull your drawer out from the cabinet. Tilt the front of the drawer at a slight downward angle to dislodge it from the railings.
Lift the drawer from the railings and cabinet and set it aside.
Mark the location of the current rails with your marker.
Locate the screws holding each rail on both sides of the drawer. Depending on the length of the rail, there will be either two screws -- one at the front end and one at the rear end of the rail -- or there will be a third screw in the middle. Unscrew each from its position.
Align the new glide to match the holes for the system you removed in Step 4. Using the new screws supplied with the new system, secure each rail in place following the instructions for the system, which may require you to pull the glide out in order to affix a screw.
Place a moderate amount of weight on the glides making sure they are firmly attached. Reinsert the drawer into the cabinet once the glides are in place.