Tampa, FL

Lay out the two support spars parallel to one another so they are about 30 inches apart.
 

Place the floor spars over the support spars, in the middle and against one another, making sure  the ends extend out from the support spars 2 to 3 inches on either side.
 

Up against the first floor spar, tie one end of the lashing rope to the platform support with a cove hitch, leaving enough “tail” at the end to twist around the long end of the rope before continuing.
 

Close to the clove hitch, make a bight in the running end and on the inside of the platform support, pass it over the first floor spar. (A bight is formed by doubling back a length of the rope against itself to form a U.) 
 

Grab this bight and pass it underneath the platform support.
 

Loop the bight over the first floor spar on the outside of the platform support.
 

Tighten both loops around the first floor spar by pulling the running end (extending between the first and second floor spars on top of the platform floor).
 

Repeat this process for each floor spar until you reach the other end.
 

Secure the running end of the rope to the other end of the platform support, with tight half hitches.