Have you ever coped trim? Some of the trim in my new workshop needed to be cut to length due to my rearranging of some of the walls. In the corners trim should be coped and not just cut at 45 degrees.
One side of your baseboard trim is cut straight, as I did here on the right side, going into the corner:
The left piece needs to be cut at a 45 degree angle with a mitre saw or a handsaw in a mitre box… I’m not sure how to explain this, but the trim edge that is cut leaves the bare unpainted mdf showing and is cut longer at the back:
Here is what the left piece looks like after being cut:
As you can see, the baseboard trim on the left will not fit against the right piece:
The next step is to cope the trim, which means to cut away the back edge, but not into the front.
I use a utility knife because this is mdf and not real wood. If you have solid wood, you need to use a small coping saw and it’s a bit trickier to cut, but still doable. With the mdf you can chip away at it.
The object is to take away all the side edging (that isn’t painted) so in effect you are taking away the back part of the trim and leaving the shaped front intact.
When you lay it flat you will see what still has to come off of the side and back edge:
This is what it will look like when the coping is finished and the piece is laying flat. You will not see any of the bare edges:
As you slide it into place:
It will fit without any gaps:
I hope this helps some of you that may have thought that coping was too hard to do… you CAN do it!