1) Carpenters, at times 2) Carpenters, sometimes 3) Roofers, at times 4) Roofers, often 5) What they learn is carpentry Found on https://www.crosswordclues.com/clue/nailers
Strips of lumber attached to the top chord of a joist so plywood or other flooring can be nailed at 36 inches maximum on center. Found on https://www.encyclo.co.uk/local/21107
1) Carpenters, at times 2) Carpenters, sometimes 3) Roofers, at times 4) Roofers, often 5) What they learn is carpentry 
Strips of lumber attached to the top chord of a joist so plywood or other flooring can be nailed at 36 inches maximum on center.