Bosch variable speed drills can double as a power screw gun by using a screwdriver bit. This lets you buy one tool and use it for two purposes. Bosch impact drills now are supplied with lithium-ion batteries, which allow for minimum self discharge and no memory effect. That means you can put the screwdriver bit and a battery in your drill, leave the drill for a period, and when you come back to it, you're ready to drive a screw.
Drill a pilot hole and then a countersink hole in the object to be screwed.
Move the reverse switch lever on the drill to the off position.
Remove the battery pack and rotate the clutch ring to "Drill." That's the icon with the drill symbol.
Rotate the chuck sleeve counter-clockwise if you're looking down the snout of the drill and open the chuck.
Remove the countersink bit and insert the screwdriver bit.
Close the chuck by rotating the chuck sleeve clockwise.
Reinstall the battery pack.
Place the screw against the object to be screwed. Hold the screw between your fingers.
Insert the head of the screwdriver bit into the slots on the screw. Allow the weight of the drill to keep the object, screw and screwdriver bit to stay connected and remove your fingers. Keeping control of the drill by holding the drill firmly, slowly press the trigger. Start slowly and increase the speed as the screw becomes embedded in the object.