Bean Slicers are tools designed to French-slice green and runner beans. They allow fast, efficient transformation of beans into thin, uniformly-cut pieces, which is important for quality, safe home canning.
There are many different kinds and models. Some are completely manual one. They are simply a handle that has an open area with wires strung through it at the other end. You press and pull the beans through the wires to slice them.
Most serious home canners, though, have always preferred the hand-cranked ones. You feed beans into a hopper while turning the hand crank. Good models can handle several beans at once. Some are designed to take the strings off the beans at the same time. Older ones clamp on the side of the table. Spong was one of the big manufacturers in North America of these. Some new models use rubber suction cups instead.
If you are doing runner beans, first pare off the stringy sides. Put a plate underneath the crank slicers to catch the bean slices as they come out.