Sail is a language for describing the instruction-set architecture (ISA) semantics of processors. Sail aims to provide a engineer-friendly, vendor-pseudocode-like language for describing instruction semantics. It is essentially a first-order imperative language, but with lightweight dependent typing for numeric types and bitvector lengths, which are automatically checked using Z3. It has been used for several papers, available from http://www.cl.cam.ac.uk/~pes20/sail/.