Sheet Bend - to tie two lines together
Bowline - to make a loop
Reef Knot - to fasten a bundle of material
Fishermans Bend - to secure a line to a post or ring
These knots are good for regular rope - braided or 3-strand polyester or natural fibre (hemp, sisal). Monofilament (fishing line) or steel cable performs better with different knots.
Knots are typically quite a lot weaker than straight rope - when rope goes around a tight radius, such as in a knot, the outside is under more tension than the inside. Splices (which require special tools, and are time-consuming to make) are stronger, so permanent fittings usually have eye-splices
Step 1: Sheet Bend
The strain is taken on the ropes in the middle - not the one coming out the side.
How the knot is made is not critical - it is the final shape that is important. One can make the flat loop first, and work the other rope around it. Or one can make the crossed loop first - required when tying a bowline.
The two images show front and back views of the same knot
Easy to make
Easy to undo when tension is removed
Does not easily capsize
Hard to make under load
Dangerous to make under heavy load
Joining two equally-sized ropes
Extending a towline or stern line
Method 1: the same as a bowline
Method 2: starting with the flat loop