How to get rusted or tight exterior nails out when hammers don't fit

What the numbers show

Counted from the threads quoted below. How we count

• This comes up 9.7× more often in r/MechanicAdvice than across the site as a whole.

1. 1
   Using a small flat pry bar or cat's claw

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2. 2
   Using a pocket knife to wedge space behind the metal

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3. 3
   Prying and destroying the old cover to access the nails directly

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4. 4
   Using a manual impact driver struck with a hammer

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5. 5
   Applying penetrating oil such as WD-40

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6. 6
   Using heat or soaking overnight with penetrant

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7. 7
   Tapping a regular screwdriver lightly on the back while trying to turn it

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8. 8
   using an angle grinder to cut through the hardware

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9. 9
   using a nut splitter tool

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10. 10
    using a torch to heat the rusted parts

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11. 11
    Soaking parts in penetrating oil overnight

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12. 12
    Heating the nut or surrounding metal with a torch

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13. 13
    Using a nut splitter or extractor socket

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14. 14
    Using an impact gun

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15. 15
    Using a breaker bar with a wrench

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16. 16
    Smacking it with a dead blow hammer

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17. 17
    Heating it up with a torch

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18. 18
    Applying penetrating fluid

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19. 19
    Using a 50/50 mix of acetone and ATF

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20. 20
    Cut the bolts off and drill out the remaining pieces

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21. 21
    Use a sawsall with a Diablo blade

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22. 22
    Heat the bolt red hot with a torch and hammer on extractor sockets

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23. 23
    Cut the exhaust pipe off and replace the entire section

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24. 24
    using a torch

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25. 25
    cutting the bolts

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26. 26
    paying a professional to do it

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27. 27
    Using a proper 1/2 drive socket instead of a flexing 3/8 adapter

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28. 28
    Heating the surrounding metal with MAP gas or oxygen/acetylene instead of propane

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29. 29
    Applying a 50/50 acetone and ATF mix for better penetration on rust

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30. 30
    Trying a heat and quench cycle or attempting to tighten the bolt slightly first to break the bond

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31. 31
    Leaving the unit alone since it is old and still working

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32. 32
    Cutting brackets or nails with a reciprocating saw or multi-tool

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33. 33
    Using a small trim crowbar between the bracket and joist

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In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.