The first two are surely levels of some sort, but they look like they can be attached to something else, something you would have on hand, or something that you could make on site.
916 looks like a tool, maybe something given away with the makers mark on it........? A tool for what, if that is hard steel, not soft, I'd say something for adjusting stuff, like...... oh man that thing just looks so familar..... looks like you would hold it with two fingers......around something.........ah...... maybe something to straighten out a bent rod of some sort...?
917 has to be attic stairs, but for a doll house
918 is a can opener, my Grama had one like that, the metal bit was SHARP and us kids were never to use it. Hers was a bit larger, for opening big cans of stuff like tomatoes etc.
919.........? Man, that one has me stumped..... candle holders that cannot fall over....?
Naw too compex..... Home made pojo sticks?
How about something like they were the suspension on a buggy seat........ but you would want four then........
Great, now this will go round and round in my head all night....