That is called 2020 T-Slot Aluminum Extrusion. I got a pack of 10 48" bars and I cut them with a hand saw. that was enough to make the two 48" long tables, but I ordered more to add extra legs to the table holding the strawberries because the water is heavy. The rails are surprisingly good at holding up that weight even without the center legs.

They are held together with these end caps and reinforced with these corner brackets. Without the corner brackets the tables were just a little wobblier than I liked. Everything is screwed together with some M3 screws.

You can probably build cheaper tables with wood or PVC, but this extrusion gives the ultimate in flexibility because I have T-Slot nuts that let me mount things to the rails. My 3D printer is itching to print brackets and mounts for cameras and such in the future.

Edit: I didn't use a hand saw. I used a Ryobi reciprocating saw, but you could do it with a hand saw.