the extension post 40 u2032 is adapted to slide onto the upper end of stanchion 11 u2032 to effectively extend the vertical height thereof from 42 inches to approximately 54 inches when installed in its functional position the lower end of extension post 40 u2032 comes into positive contact with the upper rail stop 17 a of stanchion 11 u2032 as shown in fig1 in order to attach the extension post 40 u2032 to an assembled temporary guard rail system 10 the upper side rials 16 a are detached from their position at the top of stanchion 11 u2032 by removing wing nut 20 from threaded stud 19 next the extension post 40 u2032 is disposed about the top of stanchion 11 u2032 such that the same slidingly engages internal bore 40 a u2032 and slides downwardly against the upper rail stop 17 a of stanchion 11 u2032 thereafter upper side rail 16 a is re attached to collar 18 u2032 by engaging the same on threaded stud 19 u2032 with wing nut 20 u2032 next an additional telescoping side rail not shown having features identical to side rails 16 a and 16 b as seen in fig2 is installed at the top of extension post 40 u2032 on threaded stud 19 u2032 and secured.