A specification or detailed description of something that is written out by hand or prepared informally.
Compound of 'hand' and 'spec' (short for specification). This appears to be a technical or informal term that developed in engineering or manufacturing contexts.
In the age of CAD software and digital blueprints, a 'handspec' might sound quaint, but many engineers still sketch quick hand-written specifications when you need to communicate something fast without waiting for official documents.
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