adjustable frame or ring [uh–juhs–tuh–buh l freym] noun
A professional baking tool, sometimes referred to as an extender. It is typically comprised of a 2-inch-high (5 cm) metal frame that can be adjusted to various widths and lengths. Adjustable frames come in all shapes and sizes – rounds, squares and rectangles being the most common, but you can find hearts, teardrops and other shapes, too. To use, follow the manufacturers instructions for that particular model. Some are held together with clips, others are solid pieces and ready to use.
Adjustable frames are used in two ways. Those that are meant to “extend” the height of a sheet pan are typically the same size as a sheet pan and placed along the inside edge so you are able to pour batters to a greater depth. Others are used for the shape that they create: rounds, hearts, etc. Either way, they are placed upon a sturdy, flat baking sheet that acts as the bottom, and batters and doughs are poured inside the ring. You then bake just as you would with any cake pan. After cooling, loosen the inside edges of your baked good and lift the ring up and away. They can also be used to assemble layered tortes. For instance, you would assemble your ring, place it on a sheet pan, then place layers of cake, mousse, Bavarian cream, etc. within the ring. After chilling, the ring is removed and you are left with a dessert with very clean sides.