disposable razor blades, odds are they get dull more quickly than you'd like. Instructables points us to a video demonstration showing how to extend their utility with a pair of blue jeans.
The DIYer in the video says he's kept the same disposable razor sharp for six months. How? By taking a pair of jeans and running the razor up and down 10 to 20 times in one direction along the entire length of the jeans and then again in the opposite direction. Apparently "the threads of the jeans run in a diagonal so switching directions allows for [a] balanced approach to fine tuning the blade's edge."