Some folks seem to live a perfectly happy life without knowing much about knots, but knots are very important to me.
I spend a lot of time in the outdoors.... on a boat, on farms, fishing, hunting, trapping, trimming trees, tying loads etc etc.
Here's a partial list, in no particular order, of how I've used, or might use, a knot:
Mooring a boat
guy roping a tent
making repairs to a backpack
making a makeshift backpack from a sack and some rope
temporary horse halter
stringing a bow
restraining an animal
safety line when working on a steep slope or topping a tree
making snares
tethering traps
various fishing line and tackle applications
repairing and setting a net
securing a load
hanging a lantern
erecting a radio aerial
making a ladder secure
building a shelter
hoisting objects on a building site
lifting engines etc
ensuring my boot laces stay tied properly
miscellaneous emergency repairs to fences and a multitude of other things
attaching a safety lanyard to tools where they might be lost or do damage if dropped
holding scaffolding in place
making a makeshift spear
hauling logs
hanging a game animal for skinning
towing or salvaging a vehicle
plus tying knots for practice and amusement. The list goes on.
Knots I use:
-clove hitch
-round turn and two half hitches
-Double fisherman's bend (or half of it tied back to itself for a very secure sliding loop)
-bowline
-timber hitch
-constrictor knot
-figure eight loop
-midshipman's hitch or rolling hitch or tautline hitch
-prusik loop
-zepplin bend
-trucker's hitch
-alpine butterfly or linemans loop (this is about the only knot I have trouble remembering in an emergency for some reason, so I often fall back on a simple figure eight loop).
-various fishing line knots that I can't be sure of the names of.
-buntline hitch
Interesting story about the buntline hitch. I started using a 'slipped' version of the buntline hitch to fix my trapline flags into place a couple of years ago. I thought I came up with the knot myself. I drew a picture of it and sent it to Doc. Doc sent me back a picture of a buntline hitch and asked me how to spell 'plagiarist'. I then realized that Doc had sent me the picture much earlier.... and I must have memorised the knot and forgotten about seeing Doc's picture because we'd exchanged a lot of knot pictures. Anyway, a slipped version of the buntline hitch is a very good knot if you tie it right. It holds securely, and it virtually disappears when you pull the 'slip cord' (shown below labelled 'slip knot').
Double fisherman's bend: