Installing an Acorn Thumb Latch: Passage or Closet Setup, the 37-Inch Mark and Drop Latch Sets for Pre-Drilled Doors

You have an Acorn thumb latch out of the box and a door in front of you. Two decisions come before the drill: which side of the door gets the handle, and which strike and latch bar suit the door (a passage door, or a closet or storm door). If the door already has a round hole from an old knob, Acorn lists drop latch sets made for that case.

Acorn's instruction sheets: INS25 and INS45

Acorn publishes its installation drawings as numbered instruction sheets. Two cover the door thumb latches here:

• INS25 is the sheet shown on Acorn's pages for the AT8BR smooth heart and RSCBR rough heart sets.
• INS45 covers the ATUBI heart set and the ATXBI bean set, which the sheet calls a combo set for a passage or closet door.

Each sheet also appears among the photos of the matching products below this guide. INS25 names sets by a three-character style number that matches the start of the Acorn item number, such as AT8 for the AT8BR. According to the sheet, only style numbers AT9, AT8, AT7, RTH and RUE come with all the hardware for mounting the handle on either side of the door. The RSCBR is not on that list; its own Acorn page lists a box strike, a flat strike and an offset latch bar in the set. INS45 shows both setups for the ATUBI and ATXBI.

Passage door or closet door: which strike and latch bar

INS25 shows two setups:

The flat strike plate is positioned so the latch bar drops freely into its slot. The box strike is mortised into the door stop, placed so the offset bar drops into it. INS25 groups storm doors with closet doors for this setup. Both drawings carry the same note: mount the hardware first, then locate the strike. A black nylon washer goes behind the latch bar.

Acorn's item pages put the handle rule in one line: the handle side goes on the exterior of the room, home or closet. On the inside face, a thumb hole cover with a locking button can lock the latch, and Acorn's ATXBI and ATUBI pages say the button can be left off if you do not need it.

Marking and drilling: the 37-inch mark

INS25 says to drill two 3/8 inch holes about 37 inches from the floor, or at the height you want, and 2-1/4 inches from the edge of the door, then chisel out the waste between them to make the slot. Before the handle goes on, the thumb piece is inserted through the slot in the handle until the notch on its underside drops into the locking position. Acorn notes that this keeps the thumb piece from pulling out.

On INS45, the ATUBI and ATXBI template folds over the door edge. Its LEFT and RIGHT labels refer to the side of the door where the handle mounts, its center line sits 37 inches from the floor (or at the height you want, per Acorn's pages), and it marks three 5/16 inch holes for the thumb piece slot, 2-1/4 inches from the door edge. Acorn's ATXBI and ATUBI pages then give the remaining steps, with the screw sizes for each part.

One tip is printed on Acorn's pages for all four thumb latch sets: tighten the screws by hand, not with a power tool, to protect the finish.

Thumb latch on a storm door

Check the inside door first. INS25 asks you to make sure the thumb piece, which extends 1-7/8 inches through a 1-1/8 inch thick door, does not hit the knob or handle of the inside door. If it would, the sheet says to place the two 3/8 inch holes so the thumb piece sits above or below the inside knob.

Which doors each thumb latch set is made for

Acorn lists all four sets for doors 7/8 to 1-3/4 inches thick, for inswing and outswing doors, with a box strike, a flat strike, an offset latch bar and screws included.

For these four sets, Acorn describes the surface rather than the metal: a smooth or rough texture, finished in matte black paint. The AT8BR and RSCBR share the listed size and a heart design, and their photos below show the two textures.

Door already drilled for a knob: drop latch sets

A thumb latch goes through a slot of its own. For a door that already has a round hole from a knob, Acorn lists drop latch sets for predrilled doors; its pages add that they also go on doors not drilled yet. Pressing the thumbpieces lifts the latch, and Acorn says the handles are made of heavy cast iron. The hole sizes differ by set:

All four are listed for doors 1-3/8 to 1-3/4 inches thick, left or right handed. The RUQBI is listed for the larger cross bore. Its deadbolt takes a key on the exterior and a thumbturn on the interior, with a 5 pin cylinder and a Schlage-type C keyway. Handles measure 9-1/2 x 3-3/4 inches on the RUTBI and 11 x 3-3/8 inches on the other three.

Measure the holes in your door before you choose. Our guide to bore, backset and door thickness explains the terms, and the door handing chart shows how left and right handed doors are named. Acorn's pages for these sets show no numbered instruction sheet.

Acorn at The Builders Supply

The thumb latch and drop latch sets from this guide are listed below it, and more Acorn hardware is on our Acorn brand page.

Not sure which strike, latch bar or drop latch set fits your door? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].