What does locking a page do?

A locked page keeps its drawing when you press "New designs" or change the readers, line weight, detail, trim or kinds of design. Its colors and numbers can still be made again when you change the palette, the code or your pencils (unless you colored it yourself). While a page is locked, its kind, shape, cells, new design, Edit and Change colors are greyed out: click the lock again to unlock it.