ya its birch ply from home depot. dirt cheap. but forewarned it doesent absorb a stain too easily. as far as the joints it was really a top over place and screw. i had predetermined that the granite countering would go on top so i just countersank the screws and let them be. i did some on the sides of the unit and filled those with putty. shelves are held with shelf pins on the inside and countersunk screws on the outer door side. a couple of things i would have done differenly. the molding i used was glued on with gorilla glue. stay away from this stuff for heavy application, its real messy. i should have used a nail gun and tapped and puttied. I also should have made an effort to find cheaper supplies as the perforated aluminum cost me 40 bucks and only needed a fouth of the sheet. Another thing is that i used a stain/poly combo mix sold by minwax. i would suggest to stain and poly separate. they both achieve the same results but the combo needs alot more coats to get the desired color as advertised. the granite countering was also expensive. 80 bucks for an 8x6 sheet and i only needed half of it.