The Granny Knot, also known as a Thief's Knot, results from a
second step after making an Overhand Knot. The Granny Knot is
simply the improper completion of what would otherwise be a Square
Knot. The first half of this is properly referred to as an Overhand
Knot, but is also called a Thumb Knot and a Common Knot.
So, what you have really asked is how to make an Overhand Knot.
This is formed by taking one free end of a line and going once
around the same line (often at the other end of the line) and
pulling taut. This is the first action done with a shoelace when
tying shoes.
This knot is not properly called a half granny knot, but should
be called an Overhand Knot.