Cattle panels are usually 16 feet long and about four feet tall. Bent lengthwise, you can connect them together to create as short or long of a greenhouse as you need. To build the greenhouse, you will simply bend the panels into arches, and secure them on each side by pounding in metal T-posts for them to rest against. As long as the panels are securely attached to one another, you can keep them in place by installing one T-post per panel per side. For extra rigidity and stability, you can also attach them to a 2x4 laid down on the inside of the T-posts.
Cattle panels are sturdy enough to build shelves on the lower part before they start to curve in an arch, so you can maximize your space, or build freestanding shelves and not worry about the weight.
If you need to move them, all you do is pull up the T-posts and pound them down again in a new location. They work great for animal shelters and portable sheds, too.
At approximately $20 each, you can build inexpensive, sturdy and easy to build greenhouses and other shelters for just about any purpose you can think of for your home or farm.