Instructions for Simplex Locks

This photo shows a Simplex lock.
This photo shows a Simplex lock. (Image: Jupiterimages/ Images)

The Kaba Ilco Corp. manufactures numerous sophisticated locks for laboratories, offices and other locations. The most basic of these devices are the company’s “Simplex” mechanical locks. Anyone who knows the combination can open a door secured with one of these devices by entering the combination into the simplex keypad. These devices must be fitted to a door like any new door hardware set. Installing doors and door hardware is a job full of peril and woe for amateurs, so these locks should be installed by an experienced trim carpenter. Removing them and resetting the combinations are much less subtle tasks.

Things You'll Need

  • Flathead screwdriver
  • Tweezers
  • Pen and paper

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Open the door to begin removing the lock to reset the combination for a Simplex LD450. Unscrew the two long screws on the interior lock unit with a flat head screwdriver.

Pull the lock and gasket away from the door. Set the lock on a flat surface and remove the gasket.

Loosen the four red retaining screws from the back of the lock with a flathead screwdriver. Remove the cover plate from the back of the lock.

Identify five red coded tumblers, eight blue uncoded tumblers and one clear tumbler.

Press the “C” button on the front of the lock—with the front of the lock facing down—and hold.

Remove one or more of the coded and uncoded tumblers with a pair of tweezers. Rearrange the sequence and number of tumblers to reset the code. The code may have as few as three numbers or as many as seven.

Release the “C” button. Write down the new code.

Refasten the cover plate to the back of the lock using the four red screws and a flathead screwdriver. Replace the gasket.

Reattach the lock to the door and the interior lock unit with the two long screws you removed and a flathead screwdriver.

Tips & Warnings

  • Never remove the clear tumbler.


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