The bridge from an early lyre or fidel has been found on Skye[BBC]
Interestingly the bridge seems to be flat - indicating that either it's from a plucked instrument, or that all the strings were sounded together. But what do we make of the hole through the bridge on the r/h side? I'd imagine that a drone or bourdon string fed through it? Such drone-strings were quite common on medieval bowed instruments, and were in standard use even on Welsh crwths.
I'd doubt any special apparatus was needed to hold it in place on the soundboard - the pressure of the strings would have done that alone, as on modern string instruments... where the bridge isn't tied or glued-on either.
