The denting flaw had a workaround of adding a metal edge to the wood. As a spanking implement, this was less useful as a less than perfect [[stroke]] could land slightly turned and his mostly edge-on on the metal side possible causing undesirable [[welts]], [[Bruise|brusing]] or cuts. And from a primary usage point of view, the additional expense made less the ideal, and the design made the wood/metal join not particularly long-lasting; whereas the full metal ruler didn't have this durability flaw and not only shared draws of both expense and pervertible dangers, but metal temperature expansion issue make less consistent a measuring implement.
The plastic ruler by contrast has all the advantages of cheap, doesn't easily dent, and not only doesn't have the temperature altering it measuring, but their ability to be [[transparent]] actual also makes them the superior choice for accurate measuring. This means they rapidly replaced the traditional wooden
A [[blackboard]] ruler is a larger design that sometimes includes a handle.