It always annoys me when i make biscuits or cupcakes with soft icing and i can only fit one layer in a tin - its such a waste of space! So i decided to add a shelf into one if my plastic tins. I screwed 4 screws, one on each side, in the sides, halfway between the top. Then rested a bit of cardboard covered in tinfoil on the screws. Now it has double the capacity - good times!