I have some 1-sided (top - all parts are smd) layouts that I have
prototyped by hand (laser print and etch) and will now order 'proper'
2-sided pth boards.
These boards had many top-side jumper wires, so I want to re-route them
on the underside.
However, I am unable to route on the 2nd (in my case: lower) side of the
Attempting to route an underside track produces "can't set via to layer
'16' at: <co-ords> when I try to end the trace.
I have loaded an appropriate DRC file with 2 sided copper defined but
Eagle still seems to think that it only has top copper.
What else must I do ?