If you need to add a new rope to a frame line, lay the bight on top of the line.

Bring the bight behind the frame line.

Pull the tail through the bight to form a Lark’s Head.

If you want this connection to look more like how a Cow Hitch, turn it into a Prusik Head. To do this, pull the bight out…

…continue wrapping it around the frame line in the same direction it was going…

…

…then run the tail through the bight a second time.

Tighten. This is a Prusik Head.

Here you can see a Cow Hitch next to a Prusik Head. You can see how they rhyme.