I assembled two units in about 40 minutes. A unit comes in 1 box weighing 33 Lbs making them easy to carry. This light weight is due to the shelving being skinnier than traditional 5/8" shelving, but it is pretty sturdy when all assembled. These shelves would NOT be good for damp locations like a basement.The overall assembly includes inserting tabs into slots. No screwing screws or hammering nails. As you start to assemble the shelving it will wobble and fall apart. It gets sturdier as you progress, and the assembly gets easier. When assembled you can easily wiggle the unit. I would not recommend using it where it might get rattled or pushed. It does work well for me as I placed the units in a 6'x6' closet. I would question how safe the 72" unit would be if used in an area prone to earthquakes, and I would not recommend if kids are going to be playing around it.Here are some things to note BEFORE buying/assembling: *Shelves are <.25" thick so while it brags about holding 385 Lbs per shelf, it recommends the weight be evenly distributed. *If you are making one large shelving unit you can't add shelfs where the extenders are. *If you want more than 5 shelves, reconsider this unit as while you would think there is that ability (by buying a second unit), the actual shelf is < 0.25" thick but the cross members are 2" so you lose about 11" of the 72" height. *When you open the box get ready for Styrofoam to be broken and all over (grab your vacuum--I spent more time vacuuming than assembling). *The adjustable shelves are a nice feature. You can make 2 small shelving units or 1 tall. Flexibility raises the star rating. *Wear gloves. *The only tools the instructions suggest are a flat head screwdriver to aid in pressing the tabs (I found my thumbs worked fine) and a rubber mallet (you can soften a regular hammer with duct tape--that's what I did because I couldn't find my mallet) *Angle irons wiggle when you are starting the assembling so if you don't have a helper, protect your walls with socks on the ends. *Assemble the shelving in its final location because you can't move this unit without it falling apart. *This shelving will need to be un-assembled and reassembled if you need to move it. This and the previous point are why I am giving it a low rating on Maneuverability. *The instructions that come with the unit are vague. In the Q&A area I have provided 10 Steps to Get you Started. This is the reason for only a 4-star rating. Once you get an understanding of the assembly it is easy to do and you can do it by yourself with some ingenuity.PROS:-Great value for the cost.-I liked the ability to customize where I wanted the shelves.-It holds a decent amount of weight and the shelves are a good size depth and width-Simple assemblyCONS:-Understanding how the unit assembled had a learning curve but was simple once I realized how it went together.-It cannot be moved once assembled.-It is not sturdy in the sense that you can easily wiggle the 72" unit. And, the 36" units also give a little when pushed.