Baking tin size might seem flexible, but in most cases it’s not. A smaller tin may not hold all the dough and filling to be baked and a larger one will cause it to be spread too thin. Sandwich tins are round tins that are 3.75-5cm deep, sometimes slightly shallower. For rectangular tins, I use 33 x 22.5 x 5cm baking tins, 38 x 25 x 2.5cm Swiss roll tins and 36 x 28 x 2.5cm baking sheets.
In addition to baking biscuits and cookies, flat unrimmed baking trays are useful for moving dough and cake layers and for chilling pieces of dough.