A sliding door will be out of alignment with the frame when the rollers need adjusting. The lock will not meet up with the frame latch unless the rollers hold the door the correct height. The patio door will meet the jamb at an offset angle if one roller is higher than the other. Sliding doors that are misaligned often have trouble rolling which also makes them difficult to open and close. Adjust a patio door to make it fit properly and roll easily.
Locate the set screw for the roller and determine if it has a Phillips or slotted screw head. The set screw for the lead roller is on the lower edge of the sliding door frame that meets the jamb. The trailing roller set screw is at the lower edge on the opposite side of the frame. Most door frames have two screws on the bottom edge. The upper of the two is for adjusting the roller. The lower screw holds the frame together.
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Raise the door. Insert the appropriate screwdriver type into the head of the set screw and turn it clockwise to raise the door on that side.
Lower the door. Turn the set screw counterclockwise to lower the door on that side.
Align the adjustments. Set the two rollers to position the door at an equal height on both sides for easy rolling and correct fit. Be sure the lock mechanism is at the proper height to fit the latch. Make minor adjustments if necessary to compensate for a door jamb that is not perfectly plumb.
Clean rollers with a spray lubricant to make rolling even smoother. Older sliding door rollers were made with metals that can rust. Replace the rollers if the set screws are rusted stuck.
Never turn the lower screw holding the frame together while the door is upright. The frame can come apart and release the glass. Stop turning the roller set screw counterclockwise if it starts to back out of the slot. That means the roller adjustment mechanism is frozen. If the screw comes out entirely, the adjustment mechanism will come loose and allow the door to drop on that end.