The process of hechsher keilim, colloquially known as “kashering”, can be deceivingly simple, but the application is not always as straightforward as it seems. Shulchan Aruch describes how to kasher an oven and counter, but how does that apply to contemporary ovens coated with porcelain enamel or countertops made of Corian? What about a microwave, dishwasher, or dentures? And things become even more complicated when dealing with homogenizers, retorts, and other industrial equipment. This work analyses the halachic underpinnings of the halachos and combines that with relevant descriptions of equipment, to lead the reader to informed conclusions.