Screws.
 

Screws, in more than one meaning!
First, why, oh why, have differente type of screws in your engines... like... cylinder head screws are hexagonal, carburetor are phillips, mufller are ... one or the other...
Second: I have a new engine, flown one season, I CANNOT REMOVE ONE OF THE CARBURETOR SCREWS. Please, what do I do??????

Screws.
 

We don't know how O.S. decides upon what type of bolt/screw to use. Possibly availability and price. Also the crosspoint carb retaining screws don't protrude as much as a socket bolt.

The main problem in dealing with the carb screws is the fact that American Phillips screwdrivers are too pointy. We've have to blunt the nose of a #2 Phillips screwdriver on a grinding wheel so that it fits the head of the screw properly. With a properly-fitting screwdriver, they come out easily.