This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
To overcome the difficulty of skis slipping back when walking uphill either of the two devices shown is good, if the attachments are fastened to the rear end of the skis.
The first represents a piece of horse-hide, about 4 in. square, tacked on the ski and with the hair slanting backward. This will not interfere with going forward, but will retard any movement backward.
The other consists of a hinged portion that will enter the snow on a back thrust. As the ski end is thin, a block of wood must be attached to it on the upper side, and the projecting piece hinged to the block. The bevel at the end allows it to dig into the snow when the ski starts back. In going forward, it will swing out of the way freely.