Extra anti-slip strips are glued to the bottom of the sliding board.
Sliding board model: Easyslide
Especially during steep transfers upwards it is important for the board to sit in place just at the edge. The disadvantage is that it is more difficult to put the board in place under the body. The user’s solution is to lift up one leg and place the board on the cushion instead of pushing it in.
handicareusa.com (last checked June 2020)
This tip is from 2010