There is an idiomatic expression, “like a hot knife through butter,” indicating something that is extremely easy to do.
Yet, somehow when people make toast, they frequently use a COLD knife (or at least, a room temperature one) to cut a piece of butter.
This is particularly troublesome if butter is stored in a fridge, in which case the butter-er has a cold-knife-plus-cold-butter situation on their hands.
In Figure 1, we see a regular pop-up toaster. Now, note the minor yet game-changing innovation in Figure 2: a special slot for a knife to rest in while the toaster operates.
This slot isn’t powered: it is just in proximity to the toaster’s heating elements. Thus, it doesn’t consume any additional electricity (and is unlikely to electrocute the operator).
One issue here is that we want the blade of the knife to get hot, but not the handle. It is possible that an insulated / plastic handle would be sufficient to solve this, but that does mean that this type of toaster wouldn’t be especially usable with just any old butter knife. Or the user could use an oven mitt to hold the knife.
PROS: This system operates entirely on the “waste” heat from the toaster, so it’s a zero-cost way to improve the toast-buttering experience.
CONS: Encouraging people to put metal cutlery into a toaster may increase the toaster-related-electrocution rate.