Unlike most “contour sanders” which can change the shape of the material as you work, this one holds sandpaper in exactly the profile you set. It works just like a contour gauge, but with sheets instead of pins so it can support sandpaper.
To set its shape, just loosen the two side screws and press the inner sheets against your desired curve. Then tighten the screws to pull the sides together and lock the sheets in position. This particular model is designed for sanding on model airplanes, but it looks big enough for some furniture detail applications, too.
Street pricing starts around $10.