We make our sailors valentine boxes with eight pieces of trim that hold the glass in place in the box. Unless you request loose fitting glass trim, we do our best to provide tight fitting glass trim.
Tight fitting trim will generally hold the glass in place without being glued or tacked into the box; however, if the humidity level in your home is extremely low, then the glass trim will shrink faster than the rest of the box and could become loose enough that the glass would fall out of the box if you have it hanging on a wall in your home. For that reason, once you have completed your sailors valentine, even with tight fitting trim, we recommend "tack gluing" no more than every other piece of trim into the box using a tiny dab of clear silicone near each end of the trim piece. Some of our customers have found that a single dab of silicone on only the top piece of trim is all that is needed on our boxes with tight fitting trim. The advantage of silicone over wood glue or all-purpose glues like 527 or E6000 is that you can more easily cut through the silicone with a sharp blade if you're unable to pop the trim pieces out of the box.
IMPORTANT: If you apply too much glue to the trim pieces, you may be unable to remove the glass without damaging the box.