Being a retired guy and my honey wanting garden boxes, I racked my brain to think of something I could build them out of that wouldn't send me to the poor house. (very old term) Well what I came up with was an idea that metal garage doors get run into, it usually only damages the bottom section. So you call a garage door company out and they replace the whole door. If you check with them either they will give them to you or you could pay scrap metal price for them, or maybe a portion of that on a good day. Now what I am talking about is the foam insulated metal doors. What I did was to cut them with my skill saw, w/metal cutting blade, to build a 4 ft. square garden box. Then I pulled the foam out of each end of each piece of the G/door that you now have and cut the foam off the width of a 2 X 8, cut a 2 X 8 the length needed to replace the foam taken from each end of your G/door pieces. You will need to have the wood in order to fasten the G/door sections together to make up the square garden box. I used a 4 X 4 cut on the bias to form a wedge in the corner that I ran screws through and into that 2 X 8 in the G/door sections. I supposed you could get some galvanized angle iron to hold everything together, instead of the cut 4 X 4's. There will be some sharp edges, so I finished off the outside corners with 1 X 6 cedar fence pieces, then cut a corner wedge to cover each top corner of the garden box. The garage doors probably won't need painted but I did stain the cedar corners. This thing looks great, most doors have some kind of design on them that helps a lot with the look. I did make 4' X 4' boxes but if I were to do it again, I would do a 4' X 6' box. the g/door sections are strong enough to hold the dirt. Well now I should talk about the dirt. These boxes are about 18" high, that's a lot of dirt, what I did was, I filled the bottom half with shredded tree branches, there was a place near by that the city took downed limbs and there was a huge machine that smashed them up. This was free for the taking. then I ordered a garden mix to finish filling the boxes with, it was peat moss, compost, vermiculite, sand and top soil. Years after I put it in there you could just plunge your fingers into it, Don't need no dang tiller. I got some metal posts like they use for stop signs and fastened them on one end with fencing material attached for things to climb on, green beans etc. These posts also get screwed into those 2 X 8 pieces, they are very useful. This is a secret that we will need to keep within SMF so there isn't a run on used garage doors. LOL Actually I have not shared this with anyone but family and so that continues.