The Zeppelin Bend is a secure knot for joining two lines together that can be loaded before it is tightened.
To Tie a Zeppelin Bend:
Hold the two working ends alongside each other, both pointing in the same direction, like shown in the picture.
Tie a half hitch in the nearest line so that it encloses the second line, as shown in the picture.
Bring the standing part of the second line away from the first line in the opposite direction and across the second working end, as shown in the picture.
Bring the working end of the second line through the loop in the first line and through its own loop (like shown) forming two interlocked overhands. Tighten the knot slowly by pulling on the both standing parts.