Puzzling through the diagrams and descriptions of knots in a book may be good for my mental fitness, but Alan Folsom’s animations make the whole thing easier to grasp.
Of course, I still enjoy the flavour of the Admiralty Manual of Seamanship (my copy, a hand-me-down from my father’s father, is the 1915 edition). Here is what it says about the Sheet Bend:
Sheet Bend (or Swab Hitch).—In making a bend the ends of the two ropes are not used simultaneously as in forming a reef knot, but an eye or loop is first formed in the end of one of the ropes, as in Fig.1, and the other rope’s end is then rove through it in various ways according to the bend desired. Used for securing boat’s lazy painters to the Jacob’s ladders of the Lower Booms.
To form a Sheet Bend, pass the second rope’s end underneath the eye at point a and bring up through the loop, then form with it a half hitch round c and b (Fig. 2).
It will hold still better, and is less likely to jamb, if the end is passed round again as in Fig. 3. This is called a Double Sheet Bend.