Mechanical and outline layer

By default, all printed circuit board mechanical layer and keepout layer (protel software) will be milling or cutting treatments. Do not use mechanical layer to defined any copper line or silk characters.

How to using PCB mechanical layer

Defined a pcb board outline layer, You can use mechanical layer, The protel software is called keepout layer.

Defined Non-metallic annular slot, Please use the mechanical layer. Any other layer's hole will be metallized. Or may even be ignored.

A few of non-metallic hole

If you want to add a few of non-metal hole, you can add an new mechanical layer to define. And named the new layer as "NPTH (non-plated through hole)".

Do not use silkscreen layer to defined any slot or annular sign(annular mark).

Note:
DiGPCB's manufacturer minimum annular slot distance: >= 0.8 mm, minimum drill size: >= 0.3mm (mass production)