I would like to know what kind of metal is the screw in driftwood that keeps it screwed to the slate?I would like to know 'cause the one i have is a square head and my square bit is stripped!!I also need to screw another peice of slate to it for it is a bit too waterlogged to sink!I need to know what kind of metal it is so when i get a replacement it wont rust!!I also wanna get it in philipps head so it wont strip again!! Thanks Guys