A sliding patio door that's not level is an annoyance you have to deal with every time you open the door, and an embarrassment whenever company comes over to spend time on the patio. Level the door by adjusting the height of the door rollers, or by replacing the rollers entirely. Your patio door is heavy, so don't try to remove it without help. Clear a space to lay down the door once you've removed it.
Place a leveling tool along the top or bottom edge of the door to determine which side of the door must be raised.
Raise the roller on that side on the door. A screw in a hole on each side of the door is associated with each roller. Raise the roller by turning the screw on the side of the door clockwise. This will raise the roller and that end of the door. If you are unable to level the door by adjusting the rollers, or the rollers look worn, replace them.
Remove the door from the track. The door is heavy, so do this with a helper. Grab both sides of the frame halfway up the door and lift the door up. Tilt the bottom out of the track while lifting the door. If the door does not easily come out of the track, pry the wheels up with a screwdriver.
Unscrew the old rollers from the bottom of the door and remove.
Screw on the replacement rollers. The package directions may direct you to lubricate the new rollers. Be careful not to overlubricate them.
Turn the screws in the hole on each end of the door clockwise to adjust the rollers.
Lift the door and set the rollers in the bottom track to put the door back in place. Have your helper assist you.