Placing items such as cookies or scones on a baking tray in an interlocking pattern can enable you to bake more at a time, and with a more evenly shaped result.  As the cookies spread, if not interlocked, they may spread into each other leaving you with blob shaped cookies.   Interlocking makes the best use of the space on the cookie sheet so you can fit the maximum number of cookies on the tray and still have then be nice and round.