A screwdriver is a tool used to install or tighten screws.
A typical screwdriver consists of two parts, a handle that is often made of plastic or rubber, and the metal blade. The tip of the blade is usually made of harder metal, so that the head won't get worn out too fast. While the screwdriver is usually used as a tool, it can also be used as an improvised melee weapon. A power drill can also be used to install or tighten screws, and since it's battery-powered it is less straining to use. (SG1: "Prometheus", SGA: "Tracker", SGU: "Pain", "Pathogen")
After Dr. Jennifer Keller had accidentally fried Kirykˈs Transporter wrist device, she gave it to Dr. Rodney McKay who was able to repair it using a screwdriver, and possibly some other tools. (SGA: "Tracker")
Dr. Nicholas Rush used a screwdriver as a weapon when he was being stalked by MSgt. Ronald Greer, who was being affected by an Alien tick. He later stabbed Camile Wray with the screwdriver believing her to be a Nakai, as he was also under the affect of the Alien tick. (SGU: "Pain")