This is a home made safety switch inspired by this web page: http://rick.sparber.org/ssw.pdf Where his is made from MDF, mine is 3d printed. I included the Solidworks 2011 files in zip format for those who can use them.Print the two parts, assemble with two 6-32 screws 3/4 inch long, as in the photo. The holes should print for self tapping. Mount to your Decora switch making sure it is right way up. See the PDF in the link for more information. Paint it or print it in red for the traditional safety switch look.