Which type of tool fits into a recess in the head of a fastener?

The tool that fits into a recess in the head of a fastener is the screwdriver. This is because screwdrivers are specifically designed to engage with the various types of recesses found in fasteners, such as screws. The tip of a screwdriver is shaped to match the profile of the head of the screw, allowing it to turn the fastener either to tighten or loosen it effectively.

Screwdrivers come in various forms, such as flathead and Phillips, each designed for different kinds of screw heads. The ability of the screwdriver to enter the recess and engage with the fastener makes it the most suitable tool for the job.

In contrast, tools like ratchet wrenches, pliers, and impact wrenches do not fit into the recesses of screws but instead are used for different types of fastening or fastening applications, typically involving nuts or bolts rather than screws.