A skid is a single-deck loading platform which lacks a bottom deck. It is a low-profile mobile platform which simply rests on pedestals attached to the deck.
When defining a Pallet or Skid, you need to specify the weight of the Pallet/Skid itself as well as the total weight it can carry.
You need to also set the Width, Height and Depth of the empty Pallet or Skid itself.