How to fit a door stop to an internal door frame 

If the frame has separate stop pieces, which most internal door frames do, you'll need to mark where they go and attach them, usually with nails. The stops are what the door will sit against when it is closed. There are usually three stop pieces, for the top and both sides of the frame.

Step 1 - Measure the thickness of the door

To position the stops correctly, you need to know how thick the door is so you can work out where it will sit when it's closed. It's best to measure in a few places along the edge of the door in case it is not a uniform thickness all along the edge. Use the largest of the measurements as your guide. 

Step 2 - Mark where the stops will go on the frame

Measure from the edge of the frame that the door will sit flush against when it is closed. Mark for the thickness of the door, on the jamb where the door handle will meet and also on the headpiece. Mark a few places along the frame pieces. Use a set square if you can so you know the marks are all the same. 

Add about 1.5mm to the measurement when you mark it on the hinge jamb. This makes allowance for the corner of the door, on the hinged side, clearing the stop when it's opened and closed, ensuring it won't bind. These marks will guide where the stops need to be positioned.

Step 3 - Trim stops to size

Measure the inside of the frame head for the length of the top stop piece. Then measure the height of the inside frame and take off the thickness of the stop pieces, and allow for any flooring. Trim the pieces to size if necessary. 

Step 4 - Fix stops in place

Place the top stop pieces against the guidelines and fix into place. You can use wood glue as well as nails if you prefer. Make sure the pieces are straight and level; use a spirit level to check. Once the door is hung it should close perfectly against the stops.