Becket Bends
The sheet bend is the basic know most often used to join two lines end to end, but when one line has a loop or eye there is only one end to work with, and that is when the single becket bend (left) is used instead.
The end of one line is threaded through the loop as shown. If the lines are uneven in size, or if the lines are slick so that the know is more likely to slip, then the double becket bend (right) is more secure. In either case, draw the know tight before applying tension.