This mod is very simple. It adds Iron Rings to craft annoyingly un-craftable items, like Chainmail, Saddles, Nametags, and Leads. It also means there is finally a use for the new Iron Nuggets introduced in 1.11.
In a crafting table, you can craft 2 Iron Rings with 8 Iron Nuggets in a circle shape. However, you cannot craft the rings back into nuggets. You can smelt them down to reclaim only one nugget, though.
If you put Iron Rings in the armor shapes, you can craft Chainmail armor, if you want Chainmail for whatever reason. If you really need armor right now, but you only have 4 ingots, that's still enough for a Chainmail Chestplate, which is much better than Iron Boots.
Saddles, Nametags, and Leads have unshaped recipes. Saddles are 2 Iron Rings and 1 Leather. Nametags are 1 Iron Ring and 1 Paper. Leads are 1 Iron Ring and 2 String.
I may add more to this mod in the future (like spring blocks or other types of rings), but for now it is a simple vanilla-style addition for your convenience.