Somebody may not know the different between counterbore and countersink on PCB.
Both are used to mount nails to keep the PCB in the suitble position.
The cross-section of the counterbore looks like letter “T”, but the countersink looks like a funnel.
Pls see the below picture:

PCB counterbore

PCB countersink
Pls visit our website if you have more questions about PCB.