Metal Bottle tops are readily available anywhere soft drinks or beer is sold, and are a good source of thin metal. The metal can be bent ,cut, holed, flattened and joined.
Care should be taken as the serrated edges can be sharp, the cut or holed edges are always sharp.
Flattening bottle tops is best done with a hammer(stone) and a hard surface, wood will do.
To make flattening easier open up the bottle top by using a piece of wood with a bottle top hammerd on to the end. the extra widening of the edges makes flattening the egdes easier.
See the 'metal' section for working the metal.