9. Build Or Repair Stuff
Every since the first tools were made to create something, these same tools were used to repair what they built. Build or repair are the major functions of tools and the sonic screwdriver has no end of functions here. The Doctor builds and repairs objects quickly with the screwdriver. He pulls it out, points it at the guts of the device and it is working however he requires. But have you ever wondered just what the screwdriver is doing? Just how does it build or fix anything? When he's poking the screwdriver around the insides of some device it always reminded me of a technician using a soldering iron to solder or unsolder wires of a circuit. To this end he could be either building or repairing the device. In The Ark In Space the Fourth Doctor repaired the air circulator before they all suffocated after he found the circuits had be sabotaged. Since then, the Doctor has built or repaired a multitude of contraptions. The Tenth Doctor, in The Sound of Drums/Last of the Time Lords built perception filters, repaired Jack's vortex manipulator, and later disabled it preventing Jack from time travelling. In the real world ultrasonic soldering enables direct wetting to 'hard-to-solder' materials and non-metallic substrates without the need for external solder. Every time the Doctor built or repaired an electrical or mechanical device he would need to unsolder or solder pieces. This function would do both.