this is the sled , the Paris not our toy sled for sand trials... :
http://www.rei.com/product/609482There are tracks at the bottom of the sled, some add metal runners too.
I have seen many very elaborate designs but we wanted something really simple , so we avoided adding metal bits , just used climbing rope,knots carabiners and PVC tubes .
We drilled the holes and put the pulling part together in about 30 minutes.
It was intended for a hike along the Skwentna river and thereabout, so mostly flat . (it is the area where the Iditarod race is run)
For the steep downhill bits we figured out that he (Yair) could let the sled down in front of him, sort of belay style.
(Yair used to rock climb and still does some ice climbing)
The system worked well.
Franco