I'm going to be trimming out a bunch of doors and windows using a Mahogany hardwood (Sepelia). It's going to be a typical 45 degree picture frame style. I'm debating on just pin-nailing the 45s, gluing them or actually taking the time to biscuit and glue. I have a plate jointer (biscuit) so I wouldn't have to buy any tools.

I know this is bordering on "opinion based" which is frowned upon here, but if I could get some advice, that'd be great.

  • Glue is getting close to permanent placement. Okay if you don't plan to be there if removal/replacement needs to be done. Would probably make the seams almost disappear.
    – crip659
    Commented Oct 25, 2022 at 21:35
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    From my understanding, a pin nail (which is headless) really has no long term holding power, and so the joint has to be glued. I've also heard that pin nailers are just to hold the trim in place until the glue dries.
    – SteveSh
    Commented Oct 25, 2022 at 23:50
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    Why don't you just use a standard 18 gauge brad into the mitered joints? I've never used a pin nailer for window or door trim.
    – SteveSh
    Commented Oct 25, 2022 at 23:51
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    A pin nailer shoots 18 gauge nails.These are usually available up to 2" length. Micro-pins are the really small 23 gauge nails you are thinking of.
    – Kyle
    Commented Oct 26, 2022 at 4:00
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    @Kyle - My (headless) pin nailer, a Grex Pinner, only shoots 23 gauge headless "pins", of varying lengths. It has no capability to use 18 gauge brads or pins.
    – SteveSh
    Commented Oct 26, 2022 at 10:56

2 Answers 2


I think gluing the miters is an excellent idea. I would use a small amount of construction glue (from a caulk gun) rather than regular wood glue which can be runny and messy. We typically construction glue baseboard miters- rarely on door/ window casing miters.

You certainly could do biscuit joints at the miters but in my mind this is overkill. The time involved is probably not worth it. It also seems like it might be a difficult fit job- especially if the flooring is already installed. That said, there is also nothing wrong with doing an overkill job when you are using expensive woods that you want to last a good long time.

  • The advantage to biscuits is that they give you a keyed alignment to help keep the surfaces flush while you align them then clamp or pin/brad nail or whatever them to ensure they don't move while the glue cures. If you're after a really precise surface, the extra time may be worth it. Also, for an exterior door, directly exposed to the weather (no overhang), I could see using a construction adhesive, but a waterproof PVA glue like Titebond III™ would be much easier to clean up any squeeze out, and should be <s>just as strong</s> sufficiently strong.
    – FreeMan
    Commented Oct 26, 2022 at 11:50
  • As far as runny glue, I've seen many people recommend squeezing the glue into a paper/plastic cup, then adding sawdust (from the wood just cut) and mixing it in to make it a bit more paste-like. Has the added bonus of being a matching color filler for any tiny gap that may work its way into the setup.
    – FreeMan
    Commented Oct 26, 2022 at 11:51
  • @FreeMan When I glue up something like a table top, I use biscuits for the exact reason you mention: it keeps the alignment almost perfect. I pre-finished the trim, so wiping up any squeeze out should be pretty painless. Once cut to size, it should only take a minute or so to cut the 4 slots for the biscuits. I too like Titebond II and III and have used it a lot. III is becoming my favorite because it has a bit longer open time than II. Commented Oct 26, 2022 at 15:32

I'd have a look at some of the modern high-grab glues - the popular UK one is called No More Nails, which is a fair description.

Glue, fit, wait til it dries. You do get a few minutes of adjustment time, but it won't move when you let go, assuming your fit is good.

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