NEC PowerMate V486 Series Manual page 150

Partially insert the module pins into the socket holes.
Check that all pins are correctly inserted into the
holes and that none are bent.
To avoid bending any pins during insertion, use
equal pressure on both ends of the module. If you
bend a pin, straighten it carefully.
5-34 Adding Options
!
CAUTION: Pins bend and break easily.
Checking pin alignment