This is a tip for loosening a frozen bolt that has no clearance to whack with a hammer or put a 6 foot snipe on. You may need to pull out this hack once or twice a lifetime, but it doesn't cost anything to file away for later. Actually, there's a number of tips in this vid:
1. Nasty job? Try to get somebody else to do it.
2. Mod an air hammer bit so it engages on the side of a wrench.
3. Check if bolts are re-useable by running a nut up the whole length of the threads. If it does, the bolt isn't stretched.

Long term projects:   / ave  
Get your shop ruler here: https://www.etsy.com/ca/listing/46420...