In article , Space
writes
leave the hose pipe out over night in the shape that you want and it should
leave an impression in the grass

Or do what the experts seem to do. Use the hose pipe lay the design then
dribble sand along the line. This should stay whilst you are digging and
will be evident for a while

--
Janet Tweedy
Dalmatian Telegraph
http://www.lancedal.demon.co.uk