Pull the drawer partly out of the slot. Position the drawer runners between the drawer and the sides to see how much adjustment is needed for space for the runners.
Pull out the nails that attach the drawer’s side boards of the drawers, or unscrew the screws holding them together using a drill. Set them aside for the reinstallation process.
Reposition the drawer’s side boards in positions that leave exactly enough space for the drawer runners to smoothly operate on either side. Reattach the drawer’s side boards with the original nails or screws, redrilling holes for the screws if necessary with the sides in the new positions.
Position half the drawer runners against the outside of the drawer side boards. Mark the attachment holes for the runners against the drawer boards. Remove the drawer runners.
Drill out the holes for the runners. Reposition the runners and attach them in place with three-quarters inch wood screws through each hole.
Set the drawers in their original positions and match the other halves of the drawer runners against the boards that frame the drawer. Remove the drawer. Mark the locations of the attachment holes for the other half of the runners. Remove the runners. Drill out each hole. Replace the runners and attach them with three-quarters inch wood screws.