epidemic

No, it's not glued. You can buy polyethylene welding rods in both high and low density.
Ther enclosures are actuually welded, using the welding rods and heat, not glued. You can also use a spin welder to create a friction weld or microwave welder, though the latter is quite expensive.
HDPE is much like using wood, cuts and drills the same and it can me welded much like metal, but it doesn't rust, warp or rot..

Best regards,

Jeff Snodgres