A hollow core door is more commonly found in interior doors as opposed to the exterior front and back doors. This is because solid core doors need to be strong and withstand any attempts by individuals to gain unauthorized access. This is not the concern with an interior bedroom or bathroom door. Therefore, they are naturally lighter and present some challenges to you if you need to cut a hollow core door.
Make several measurements of the door and mark the measurements with a pencil. Use a straight edge and utility knife to score the marks before making your cuts. The markings need to be precise since you only have about 1 to 1-1/2 inches a room to play with, depending on the door you are cutting.
Make a Cut
Attach a straight edge to the door using a C-clamp on both ends behind where the scored cut line has been marked. This will provide a guide for table saw and prevent you from removing too much of the hollow core door. Cut carefully along the score line with the table saw. Cut on the solid edge and be sure not to take more than 1 to 2 inches. If you take off more than this, the door edge will become frayed and it will look terrible.
When you have completed the cut, sand the edge and fit the door in place to ensure that the cut was accurate. If you measured correctly to begin with, you should only have to make 1 cut.