Hours? Use the search function, or google or your brain, for god's sake. There was a thread with the title "Zipline" on the first page yesterday. It can't be that far down the line at this point.
Also, you'Ve got a major, MAJOR flaw in your designs.
Your zipline recipe? 4x4... the grid is 3x3.
The... "grab thing"? is 4x3... the grid is STILL 3x3.
Neither of those would work then. Pay attention next time. Plus, I wouldn't trust something made entirely of sticks to hold me up over a chasm/valley that happens to be 20 blocks deep at the least.
Not thought through. And you didn't even explain how to place the zipline either. You just said there'd be a zipline, and a "grab thing"... If you can't even remember the names of the pieces needed for your idea, then methinks you should do some more research, or better yet, GTFO Minecraft.
Well, there's actually a search function, and it's sorta the rules that you've got to use it before posting. Just a little. And it HAS been suggested before.
Also, a problem with your suggestion... since when do we have 4x4 and 4x3 crafting grids?
It's not well explained or thought out, either. Pictures and a description of exactly how it would be used are needed.