If you're faced with a rusted or difficult to remove screw or bolt - you'll need an extractor set. After using a power drill and the correct size and type of bit - you drill a pilot hole into the broken bolt or screw.
Once you've worked the hole large enough to insert the bolt extractor, making sure you've got a good grip then start turning it counter-clockwise. The extractor will tighten up inside the bolt, allowing you to work the bolt out of its position.
A specialist tool and incredibly handy when faced with a range of broken screws, bolts, hex screws and more - the five featured below are the best selling extractor sets. They're all highly rated and offer great value for money.