They are relatively labour intensive. Some people who have purchased them don’t use them much, either because they got discouraged with the technique, or found that they didn’t need or have the time to make the decorative garnishes very often.
You need to use fresh vegetables, not canned or frozen. The vegetables have to be firmer ones such as zucchini, potatoes, cucumbers, summer squashes, onion, beets, radish, etc.
The device consists of a container whose lid has a crank on it. The crank is attached to a plunger, that both turns the vegetable and holds it in place (to stop it from falling over, etc.) Beneath the turning vegetable are stainless steel blades. One blade makes thin strand slices of vegetables, another makes thicker strands. You press constantly downwards while turning.
In the upright models, there’s a bowl that catches all the slices. On top of this, you place the “layer” that holds the blade. In the centre of this layer, there’s a centre pin that you seat the vegetable on, pressing it down a bit into the pin so that it will stand up being held by the pin. Then you attach the top cover part with its lid and handle. A selector switch on the side allows you to choose whether you will be making strips, or slices.
Another version is turned on its side. You attach the vegetable horizontally, and the slices fall onto a plate or work surface. Some horizontal ones may come with a table clamp.
All models are dishwasher safe. One popular model is called the “Saladacco”
You can take the blades out of the plastic layer and sharpen them.
These devices are popular in Japan.
Most people require a learning curve to get the hang of how to operate it. Zucchini and cucumbers must be straight ones, not curved ones. Older zucchini and summer squash has more seeds in it that might interfere with the operations. Seedless cucumbers better than regular ones. The item going in needs to be at least 1 inch (2 1/2 cm) wide. For carrots, use the wide ends, not the narrow tips. Cut veg such as carrots and zucchini into 3 1/2 inch (9 cm) lengths first. All cuts that you make in your prep need to be straight, not slanted. Very thin pieces of vegetable can be laid on their side and fastened on the centre pin, and turned to make short strands (you won’t get long strands.)
You use one hand to hold the entire device stable. Use the other hand to turn the handle with the palm of your hand while pressing down. Pressure needs to be constant and consistent to produce strands, as opposed to shreds. Then remove the lid and the blade layer to get at the bowl where the results of your work are.
There will always be a small bit of your vegetable left when you are done. Discard or think of some way to use the ends of vegetable left on the blade, or just pop them in your mouth.