The sonic screwdriver is a piece of gallifreyan technology used by many people in the universe. A multifunctional tool, the sonic screwdriver is often used by the Doctor for a multitude of purposes, though it is proved to be ineffective against wood. The Doctor’s sonic screwdriver is often redesigned at every new incarnation, though they all maintain the same software. An exception to this is the Thirteenth Doctor's screwdriver, that was constructed with an unique software made from existing 21st century technology because she had lost her previous screwdriver. Besides the Doctor, River Song and Madame Vastra also have sonic screwdrivers that were gifted to them by the Doctor, and Time Lady Romana made her own screwdriver once.