I love these crates as an amp stand! They also work great for monitor wedges. I’ve been using the same four crates since the mid 90s. They are very stable, and lock together to make a higher stand. They could also be used to carry things such as cables, effects pedals, etc.
The best thing about these crates is how they fold up. No bulky metal mic stand affairs. These things fold and stack together taking up very little space. They are very easy to transport. There are lots of other manufacturers, but I can only speak for these. If I lost them, I would buy the same things again.
Pool whale alternative crate. These are also good, but will not stack with the Schiffmayer crates.