In article ,
John C wrote:
What size of nail is reccomended for nailing two 50mm pieces of wood
together. My drawing states 4mm ring nails but is there a rule of thumb on
what length to use.

The "rule of thumb" about things to be hit with hammers is quite simple:

DON'T!















hit the nail on the thumb, that is.



For a serious answer, barring special circumstances, the nail has to go
all the way through the 1st piece of wood. This places a 'lower bound' on
the length. And you _don't_ want it to go all the way through the 2nd
piece -- because then the point would be sticking out. this places an
'upper bound' on the length. A "split the difference" approach works
just fine, between those limits.