Deema's Loading Docks is the shop segment from the episode: Humunga-Truck!
Deema goes to a truck loading location and Gil comes to pick up all the toy trucks. Deema doesn't think they will all fit, so Gil mentions he can make them fit by just moving around some things. And so, he and the little fish carefully fill in the empty gaps with the boxes that match the same shapes/sizes. With the rectangle, they combine two normal square boxes, with the boxes now fit into the truck, Gil closes the trunk and drives off as Mr. Grouper says it's Lunchtime.