This is a flat, horizontally positioned cast iron plate, polished on one side, employed for rolling a glass pea to create a uniformly rounded bolo. This bolo develops on a surface that has been sufficiently cooled to provide resistance to the blowing process.
In the past, it was crafted from bronze (hence the name) or marble. Nowadays, the horizontal plate is made of iron. It serves the purpose of rolling the glass bolo, which is affixed in a barrel (canna), to shape it through a technique known as "marmorizar."
Additionally, this tool finds utility in "tociar" processes, involving the manipulation of non-fused materials like grits, machie, or reeds for crafting filigree. It can also be referred to as "malmoro" or "marver."