A width and thickness detecting mechanism of a shredder includes a shredding path, a first width sensor, a second width sensor, a third width sensor, a thickness detecting module, and a control unit. A contrast material is injected into the subject. The overcoats can prevent internal chips from being damaged and suffering dust contamination during manufacture. Also shown is a locking tab manufacturing detail which creates an inexpensive, light weight, oven cavity, which is easy to clean and also permits oven cavity washing andor immersion in water.