Two seldom known knots that are very useful are called the Crown Knot and the Wall Knot. These two knots, while they appear different once tightened, are actually the same thing!
The only difference between them is which way the tails run after the knot is finished. A Wall Knot has the tails continue in the original direction of the line. A Crown Knot has tails that continue in the opposite direction of the line.
Both knots are tied by looping through the other lines, simply finishing with the lines exiting the loops in on the top or on the bottom to differentiate the two knots.
As you can see, both knots are made by looping the lines through each other, the only difference is where the end of the line exits the knot. If it is above the loop, it will make a Wall Knot. If it is below the loop, it will make a Crown Knot. When deciding which of these knots to use, it is important to know what you are trying to achieve.
If you are creating a knot in the middle of a line, a Wall Knot would be your best choice. If you are going to perform a back splice, a Crown Knot will hold the end of the line together while positioning the tails in a position, ready to bury into a back splice.
The crown knot is actually used to bind the end of a line in the Tree Surgeon's Backsplice. It positions the tails ready to bury in the backsplice. The buried tails will not budge since the spliced into the rest of the line and the knot will hold everything together, no matter the abuse that the line is subjected to.
Wall Knots are sometimes used for decorative purposes, since they can be placed inline with the cords that hang lamps and baskets inside the hull. Another decorative use for the Wall Knot and Crown Knot is to combine them.
A Wall Knot will create a nice twist in the line and secure the strands. A Crown Knot placed over the Wall Knot will create a nice button at the end of the line. The tails will be oriented back towards the original line and can either be spliced back into the line or trimmed off short.
The combination of these two knots will create a decorative button knot that can be used to secure loops and lanyards.