@calfskin: the little screw with "countersunk raised head" or "oval head" comes from the two similar strainer/butt end parts with control knob for the lower snares and canals where the individually snare wires are gliding on (4 screws in total).
The brass screw with cheese head is used to connect the two rods inside the drum with the mechanim mounted at the inside of the shell (4 screws in total).
I use the term T-rods for tension screws looking like a T and were used mostly on bass drums untill in the square headed key bolt took over in the beginning of the 90's at most drum manufacturers.