Classic channels are often single-funded. Dual funding lets both sides contribute at open. Splicing adjusts channel capacity later with an on-chain transaction without losing the channel relationship.
Why this matters
Liquidity needs change. Closing and reopening wastes fees and downtime. Splicing and dual funding are how the network becomes more capital-efficient.
Analogy
Dual funding is both roommates paying the security deposit. Splicing is adding money to the joint jar (or withdrawing some) without ending the lease.
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Common mistakes
- Assuming splice always beats open/close without fee math
- Interrupting interactive funding flows mid-protocol
- Neglecting backup updates after capacity changes
Worked mental model
Re-read the diagrams in this lesson once out loud in plain language. If you cannot explain the flow to a friend without jargon, pause and revisit Mastering Bitcoin / Mastering Lightning chapters linked in Resources. Chapter references are intentional, not decorative.
Hands-on habit
Every protocol idea should be paired with one local experiment:
- Reproduce the happy path on regtest (or Polar for Lightning)
- Break it on purpose (wrong fee, expired invoice, offline peer)
- Write down what error you saw and which layer produced it (wallet, node, mempool, peer)
That habit turns reading into builder instinct.
Glossary check
Pick three terms from this lesson and define them in one sentence each without opening notes. Weak definitions mean the lesson is not finished yet.
Resource order
Use Resources in order: narrative book chapter first, then BIP/BOLT for precision, then implementation docs for commands. Jumping straight to RPC flags without the mental model creates brittle knowledge.
Next steps
Routing: how payments choose paths across many channels.