PVC pipes in the slots for the bikes! We had the PVC lying around the basement (not sure what for...LOL) so Kevin cut them to uniform lengths and Viola! Since our rack has slots for four bikes, we have a decent amount of drying space. The only drawback over the rack we've been using for years is that we can't move it to under the awning if rain is in the forecast. Previous rack from IKEA. But I'm thinking we might be able to rig something with small tarp if we need to.