In article ,
R.H. wrote:
Just posted another set:

http://puzzlephotos.blogspot.com/

388) Spark plug gap gauges?

389) Used on recalcitrant students? Or possibly for ground-to-air
signalling, in which case it would shoot a flare or other signal.

390) Insulator?

391) Wing-Walkers!

392) Driver for turning a knurled knob

393) ?