Drag bit also named blade bit,with a TC inserts on the blades  

Usually drag bits have three wings,while sometimes people need four wings or five wings.  

Drag Bit is a common tool which used to rework operation, for drilling cement plug and sinker drilling sand bridge ,salt bridge, scraping off the dirt of casing wall and hard wax and some mineral crystallization  

Still can scraping well hole ,making the wall bright and clean ,it may used to drilling ahead in bushing and side track (can destroy the keyway is formed when side track) or drilling and rubbing the mat of perforating shell ,etc.