Storing flatwood (plywood, mdf, etc) horizontal or vertical?

I'm not sure what flatwood is but most wood is stored flat you have room. But I think many people store it on end for easier access as far as my storage both sheet goods and hardwoods are stored on end just for access and it's were it fits in my shop.

"sheet" wood was actually what I was talking about, thanks Jim.

But what I think I'm getting from someone who seems to have been at it for just a bit longer than me…is that it doesn't make enough difference for the majority of woodworkers to worry about.

I store my sheet goods one edge (No room to store flat) but if it is going to be stored for more than a few days…or if it is "Thinner" sheet goods, I have a rack in my storage room that sits at a slight angle..it holds my wood and also supports the wood and does not let it bow or warp.

i store mine standing up. it takes less room that way (only 4' vs 8') i built a designated spot for the storage with a brace that keeps everything flat