The Sources for the History of Technology

The culture of technology often is defined as a "tacit knowledge" because the artifacts seldom are followed by complete documentation, few are the technicians who complete their innovations with a complete documentation, and very rarely they tell stories of the devices they have designed and manufactured.
The need to protect the intellectual and industrial property of the innovative items and systems leads to maintain secret the exact nature of the processes. And also the patent issues play only a legal role.

(source: http://www.cognitivedesignsolutions.com/KM/ExplicitTacit.htm)

So the historians of technology, who dig under the "explicit knowledge" to discover the "tacit" one,  build and arrange their "documents" (the essential matter to make history) in several hints and signs found within:
- artefacts
- tombstones
- letters and commercial writings
- sketches
- data sheets
- catalogues
- advertisements
- novels and other literature
- notebooks
- nameplates
- interviews and other oral memories
- movies
- ...