1.14 - How to repair clothes?

[caffeine9999]

Tried all combinations of left and right clicks with boots and a flax twine, still can't figure it out

[redram]

You should just be able to left click with the twine (or full sheet of linen, which will repair 50% durability, effectively saving you a twine vs using 5 twine balls) on your cursor, and the target item can be anywhere in your inventory, or even still worn on your person, think.  It's important to note that the twine/linen must be actual held on your cursor.  This is unlike any other mechanic in the game so far, I think, so it's not obvious. 

[caffeine9999]

Then it's a bug I guess, because it's not working with a twine (didn't check linen though).

My bad, I tried it with flax fibres, not flax twine.