The Collaborative International Dictionary of English v.0.48:

Putlog \Put"log`\ (?; 277), n. (Arch.)
   One of the short pieces of timber on which the planks forming
   the floor of a scaffold are laid, -- one end resting on the
   ledger of the scaffold, and the other in a hole left in the
   wall temporarily for the purpose. --Oxf. Gloss.
   [1913 Webster]