We needed a reed switch for a project, and I usually prefer to make these types of things instead of buying them. This project takes a typical 14mm x 2.2mm NO (normally open) reed switch and either one or two tiny neodymium magnets and keeps them all secure and aligned so they will function as a magnetic switch, either an a NO or NC (normally closed) configuration. I got all the parts on ebay. The switches were US$4 for 10, and the magnets were about US$1 for 20 of each. I used old network wire and round machined pin headers (also from ebay) for the connectors. (I like using the round pin headers as simple connectors because they're quicker to trim than the square ones.) See instructions for details. The parts have think 0.2mm tabs around trouble spots - they can be easily clipped off after printing. I have a parametric SCAD file if you need different sizes -- just comment and let me know and I'll clean up the SCAD file and upload it. There's a video of how it works here: http://www.youtube.com/watch?v=r1MOFPqZxDA Requires: Instructions: To install on a door, tape the two pieces together, magnet opening up. Close the door, put the pieces at the upper edge of the door, and mark where they should be installed.