
1) Art hanger, at times 2) Builder, at times 3) Carpenter, at times 4) Carpenter, often 5) Hammer operator 6) Hammer user 7) Handyman, often 8) Hard-hitting linebacker 9) Pinner 10) Roofer, at times 11) User of spads and brads 12) Worker 
Found on 
https://www.crosswordclues.com/clue/nailer

• (n.) One whose occupation is to make nails; a nail maker. • (n.) One who fastens with, or drives, nails. • (n.) One who fastens with, or drives, nails. • (n.) One whose occupation is to make nails; a nail maker.
Found on 
http://thinkexist.com/dictionary/meaning/nailer/

A strip of wood attached to a stringer that tread planks are nailed or screwed to.
Found on 
http://www.americantrails.org/
 Nail'er  noun   1.
Nail'er  noun   1.  One whose occupation is to make nails; a nail maker.  
 2.  One who fastens with, or drives, nails. 
Found on 
http://www.encyclo.co.uk/webster/N/1

Nailer was old slang for something exceptionally good or notable.
Found on 
http://www.probertencyclopaedia.com/browse/ZN.HTM

[
n] - a worker who attaches something by nailing it
Found on 
http://www.webdictionary.co.uk/definition.php?query=nailer
 noun
 noun a worker who attaches something by nailing it
Found on 
https://www.encyclo.co.uk/local/20974

a person or thing that drives nails, as a machine that drives nails automatically.
Found on 
https://www.infoplease.com/dictionary/nailer
  No exact match found.