Replying to What technology could you "invent" 2000 years ago?

I always think about this.

What if you were transported back in time 2000 years ago?

What do you completely 100% understand in todays world that you could "invent" back then to make advancements in technology happen sooner and thus develop everything much faster in the future (todays world).
Im not talking about just drawing them on paper (like da vinchi). I mean completely design and build using the tools and materials that were present 2000 years ago.

For me,
-Gliders, most everything dealing with simple flying machines (except helicopters, fuck that)
-Gas powered engines, but I couldnt produce gas or oil(so it wouldnt work)
-simple mechanical systems such as pulleys, hoists, jacks and lifts.
-maybe even electricity with copper coils