When installing casing trim around windows and door frames the corners are normally cut in a miter. Finish nails are normally used to fasten the adjoining casing pieces to the window/door frame and into the wall structure. My question is if additional nails should be used to nail the mitered corners of two trim pieces together and if so what is the proper method to apply the nails?

Along with this is the additional question as to whether the miter joint should also be glued with yellow woodworkers glue?

  • Are we assuming that the mitering job was done well (ie, they're a near-perfect fit)?
    – Joe
    Commented Mar 18, 2015 at 14:22
  • For this question let us assume that the fit was a good one! Commented Mar 18, 2015 at 14:25

3 Answers 3


I actually thought of this question yesterday when I was replacing trim. It seems the people who built my house nailed from the top trim to the side trim. I'm not sure about gluing them, because if you need to replace one side, you may have to replace them all if you can't separate the glue joint.


I would definitely use glue. I would also use a 23 gauge pin only in event that the joint was misaligned and needed to be kept in place until the glue dries.


There will be a lot of differing opinions and methods, but I will give you mine, based on what I have gleaned from having just remodeled my own house, and also spending the last 10 years in construction and commercial millwork industry, and hearing a lot of opinions.

Yes, I would definitely use glue.

In addition, I would invest in some Collins Miter Clamps

These are invaluable for any miter joints you may encounter.

Second, nailing may be required on some joints to maintain alignment, and I think most would aim to keep those nails on the top side of the header piece of casing, primarily to minimize visibility.

But, I would next recommend investing in a biscuit joiner, and biscuit every miter joint. This will insure proper face alignment, as well as add more glue surface creating a much stronger joint, that won't require any extra nailing in most cases.

In addition, biscuits work in very think casing materials.

Beyond that, a lot of very good installers like to use the Collins Edge Pocket Jig but this really only works on thicker casings, and is more if you are looking for bomb proof casing assemblies.

  • You seem rather fond of Collins Tools. You may want to divulge your affiliation with the company, even if it's just "satisfied customer".
    – FreeMan
    Commented Sep 27, 2016 at 15:09
  • I have no affiliation, just a satisfied customer. I only have a set of the Collins Miter Clamps. I work full time in the commercial millwork industry, and I have been remodeling my own home for the past year and a half, so I do a lot of research into tools, and I also work with many different installers and carpenters who have their own experiences that I get to glean information from as well. Commented Sep 27, 2016 at 15:13
  • If you go to my profile, I have a link to my personal website. I am far from an anonymous poster. Commented Sep 27, 2016 at 15:14

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