A mechanism called a heddle stick is needed to facilitate the intertwining of the warps and wefts. It will keep the warps separated so the wefts can pass through them. The stick below serves as the natural shed separating the right and left wefts.
The shed stick creates natural shed as it separates the right (white) warps.
Note: For demonstration purposes, I will use white and blue colored warp yarns in some pictures to represent the right and the left warps, respectively. This is intended to help viewers recognize each knot is tied on two warp strings.
Strings shown below are placed on the heddle stick which separates the left (blue) warps.
Below is how the shed and heddle stick look on the loom. The four “extra” warp yarns on either side are bundled to be wrapped later, to protect the edge of the rug (known as the selvedge).
When the shed stick is pushed downward, it pushes the right (white) warps forward, allowing the weft to be run in between the warps and across a row of knots.
When the shed stick is pushed upward, it allows the left (blue) warps forward. These are being pulled by the heddle strings, allowing the weft to be run across in between the warps and the row of knots. The shed stick is moved up and down to allow access under right and left warps.