Trying to replace the solenoid, run into this. It's 8-ish millimeter, which isn't a problem, but the shape is odd. Flat sided socket won't grip it. The bolt is dished on the sides, but not like an external wrenching bolt, as a 12-side wrench won't work here.
Before I run to the tool place, what is this head called?
(pic is taken from bottom looking up, from passenger side a-arm)

 

E-8 external torx bolt... Same as the ones in the steering column that tend to come loose.

 

^The above is correct, it is torx.

 

search for inverse, inversed reverse, external .. torx

 

Lol, got it, thanks. I've got a ton of torx drivers and bits, but had to go buy an external set from China Freight. $8.59, not bad. Got the one in the pic off, but the one on the other side is giving me trouble. Had to buy the right length 1/4 drive extension. Gonna hit it again tonight.
Collecting tools, at least.

 

When you get the other out, if you're getting a replacement solenoid or starter, see if the replacement comes with bolts with regular hex heads. If not, go buy a couple. Should end up with either 8mm or 5/16" headed bolts.