Over the years, I’ve had to track down a lot of parts, materials, and tools to build labs and demonstrations. Some stuff is common and some stuff is pretty hard to source, especially in small quantities.
Knife Switches: When I was but a wee lad, every general science supply house had a selection of sturdy knife switches for use in school physics labs. Though they are crude devices, they are great in the classroom because students can see exactly what it does — not too big of a deal for a simple single-pole (SPST) switch, but great for 3-way (SPDT)and 4-way (Cross-connected DPDT) switch arrangements.
These days, what passes for a knife switch is laughable. I have several that are so flimsy that the blade has to be carefully guided home or it will bend and twist out of the way. Well, if you are willing to pay for quality,