Installing bifold patio doors in an opening can be complicated if the opening is not the correct width and height. The doors can still be installed, but modifications are necessary or the door will not work correctly. The type of gate determines the amount of the door can be modified. More material can be cut from a solid core door a hollow core door, which can only have 1-inch solid wood around the edges.
Determine how much cut. For hollow core doors, it is important not to cut too much out of a bifold patio doors. Some doors have a solid track 1 inch and others a little more. Ask your door supplier if you are unsure. Allow at least 7/8 inch of solid material to keep the door structurally sound. If necessary, cut a little from each side to avoid taking too much out of a door.
For solid bifold patio doors, the visual aspect determines how much was cut. When a significant amount of material to be cut, break between the doors to maintain uniform some lanes. Set your table saw to the desired width and cut the door. For veneer doors, make the cut in the direction of the blade cuts with a sharp knife and a ruler, as a level.