Lesson 1
Locating the Binding Point
Perform a methodical inspection to find exactly where the door hits the frame.
The visual inspection
Do not assume the whole door is wrong. Most sticking is localized. Close the door slowly and watch the gap between the door edge and the frame. If you cannot see light, use a strip of paper. Slide the paper around the perimeter of the closed door; where it gets stuck or stops moving, you have identified your binding point.
Checking for scuff marks
Look for shiny, rubbed spots on the paintwork. These indicate persistent friction. If the friction is at the top corner near the latch, your hinges are likely sagging. If the friction is along the bottom or the strike side, the door might have swelled due to moisture. Mark these areas clearly with a pencil so you know exactly which part of the door needs work before you reach for tools.