The Palette component is used to collect multiple selections, items are selected in the left column (available) and moved to the right column (selected). The component can be configured to keep the items sorted by their visible label, their hidden value, or manually sorted. Items are moved between columns using the buttons, or by double clicking.

Obviously, there's a whole lot of JavaScript running on the client side. However, there are no arbitrary limits; you can have as many Palettes in a form as you want, or have multiple forms and multiple Palettes. Tapestry uses a sophisticated method of generating custom JavaScript from a template.

You can also customize the images used for the buttons and the titles above the two selection columns.