They are called countersink because they sink into the object they are used for. The flat head also tapers along the shaft into the material.
You could turn the screwdriver anti-clockwise to remove the fastener in the material or you could use a rubber band with rough powders.
They can be used for Timber, wood, steel, and board applications.
Asons Enterprise
Razia Mansion,
No 68 & 70 Velachery Road,
Little Mount, Saidapet,
Chennai-600015
8524 03 03 03
044 4211 8931/32/33