Trimco 3920-8M- 8" Long with Mortise Strike

It is a heavy-duty surface bolt made for Dutch doors, where the upper and lower leaves need to be locked together so the pair operates as one door. The 3920-8M is the 8 inch version and ships with the mortise strike, which is the strike that mortises into the edge of the mating leaf rather than sitting on the surface. Cast brass or bronze construction, intended for commercial openings.

Throw is 1/2 inch. That is enough to seat into the mortise strike supplied with the 3920-8M, but it means the strike has to be set tight to the bolt, with a gap between the Dutch door leaves no wider than the throw will cover. Wide or uneven leaf gaps are the usual reason a surface bolt will not engage.

No. The M suffix on 3920-8M means the mortise strike is the strike option included. Trimco offers other strike types across the 3920 Series, so if your mating leaf cannot be mortised, you would specify a different strike variant instead of this one.

Length of the bolt plate is the only difference in the pair of sizes Trimco offers in the 3920 Series. The 8 inch gives you a longer mounting plate with more fastener spread, which is what you want on a heavier or higher traffic leaf; the 4-1/2 inch suits narrower rails and tighter panel work. Both use the same 1/2 inch throw.

Five architectural finishes, by BHMA number: 605 bright brass, 606 satin brass, 613 oil rubbed bronze, 625 bright chrome and 626 satin chrome. If you are matching existing hinges and levers on the opening, those BHMA codes are the ones to match against, not the color name.

Trimco lists the 3920 Series as ADA compliant. Worth noting the practical limit anyway: a surface bolt mounted high on a Dutch door leaf can put the operable hardware out of reach, so keep mounting height within reach range on any opening in an accessible route.

Solid bronze or brass throughout, no stamped sheet or zinc castings, which is why Trimco puts the 3920 in public buildings, commercial and industrial facilities, government and military work, retail, and multifamily. For a property manager standardizing across a building, the brass body plus one of the five BHMA finishes makes it repeatable across openings.

Custom options are available in the 3920 Series beyond the two catalog lengths and the standard strike choices. If your Dutch door has an odd rail height or a non standard leaf gap, that is the route rather than forcing the 8 inch standard.