Bor Nodes facilitate sidechain block production while remaining connected to the Ethereum Virtual Machine (EVM). Bor Nodes are also shuffled on a regular basis via committee selection using Heimdall Nodes (a large group of Ethereum validator nodes) in spans. Spans are precisely defined sets of blocks that have been chosen as a validator from a large pool of possible validators. Each validator in a given span has voting power. The strength of that power determines block producer selection, with more powerful spans being more likely to be chosen.