Planter Footer

I recently purchased two [raised planters from Gardener's Supply Company](https://www.gardeners.com/buy/grow-box-planter-box/8610894.html). Upon assembling them, I thought the aluminum legs might scratch up the porch that I was going to place them on. I therefore set out to make some footers. However, I had an additional though. With the [Self Watering Inserts](https://www.gardeners.com/buy/self-watering-insert-for-2x4-planter/8609009.html) I also got, I figured they would work best if the planters where level. Therefore, I added to the model the possibility to add a little extra lift in some the the footers to aid in leveling my planters.

Looking at other planters from [Gardener's Supply Company](https://www.gardeners.com), the use of the aluminum rails appear to be a common design, therefore these footers should be usable some of there other planters.