Hollow profile polypropylene board is waterproof and semi flexible. Rot proof, puncture & injury resistant not affected by chemicals agents. Stores flat,easy to handle, easy to apply as a protection to the waterproof membrane: on top of hot asphalt before it cools down; by lightly torching and pressing; by solvent based glue. Also disposable with a bituminous side integrated thus not requiring any further protection media and saving material and labour time costs.