As the Ethereum ecosystem grows, a very popular option for building new technologies is to build a custom network, or a sidechain–in other words, another blockchain or network that is compatible with Ethereum–and then allow users to transfer tokens, or value of some kind, between the networks.

There are many prominent examples, and as Ethereum scales, they will no doubt grow and evolve. MetaMask has been, and continues to be, a crucial linchpin allowing users to move more or less seamlessly between networks.

That said, there are some significant, and common, pitfalls when dealing with sidechains that you want to avoid. The present article is written to be a non-definitive guide to best practices when dealing with sidechains. We can’t hope to capture all the nuances of dealing with every instance of every sidechain; the following are general guidelines. Troubleshooting tips are further down.