As we are moving and are going to need to create more storage on shelving we have. Since we have purchased shelves at different times from different places they are different. I had to come up with something. This series of pictures is of what I came up with.
I decide to use a half lap joint on the sides to the front and back. Then we decided to have a lip around the shelves so that the items would not get pushed off the back and or sides. We used 1x6s for the sides and back. Then I used a half lap that is similar to a mortise for the to hold the front board which is a 1×4. I added a 2×2 to support the shelves. The sides are secured to the using number 10 t-nuts. I did recess the back of the t-nuts so that they do not interfere with the front and rear boards.
It is a simple design but took me a lot more time then I thought it would. I did not use ant exotic tools. Most of the work was done with my cordless circular saw.