when trad , i made up a board, 2 ft scaffold plank , length 3 x 2 attached with screws ( for ladder to but up against ), several 6 " nails through scaffold board ,
in line with where ladder will sit,
these protrude out the other end , position on decking so ends of nails go through gap between decking, worked well,
only worked though where decking ran the right way.
daz