I used these brackets to build a firewood rack.  These brackets are very easy to use, however I found it rather difficult to make sure the vertical 2x4's were in fact plumb. This required some clamping (etc) before drilling holes for the bolts.  I haven't yet stacked wood on the rack, but I'm certain the weight of the wood will cause the vertical 2x4's to lean out.  To counter that I added a frame of 2x4s on top that will provide much more support as well as a pitched "roof."  For the price this is a good value, although, like I said, it does require some extra work if you want something really solid.