Reverse slot head screw

[monkeyspanners]

Had to strip a replacement pump motor yesterday to rotate the pump so the delivery pipe lined up with the one it was replacing.
The motor end bells were held on with four long bolts about 4mm diameter, the problem in undoing them was the heads instead of having a female slot for a screwdriver had male piece sticking out which would require a female slotted driver to undo it. (no picture as was in a rush to get the machine working again)


Any idea what this style of drive is called?

 

[monkeyspanners]

Would need a socket a bit like this Snapon shock absorber one but smaller and narrower.

https://www.ebay.co.uk/itm/Snap-On-...314455&hash=item5b4cae4b3b:g:gnEAAOSwa5lbpWS~

 

[F124C]

According to member 'erswill' who answered a similar question in the recent thread "Odd screw", it's called a Double D Socket.

AL.