Abstract: A yarn winding bobbin is disclosed which includes a tubular wall composed of wound paper layers, and a yarn catching slot positioned adjacent one end of the tubular wall. The slot includes an inlet portion and a clamping portion, and the inlet portion includes an opening which extends completely through the wall. A yarn trap is formed in the opening for engaging a yarn which is positioned to move in the direction of rotation of the bobbin. The yarn trap is configured in such a manner that in the event of a suddenly occurring force exerted on the yarn, the yarn trap will not be destroyed. This is accomplished in that the yarn trap includes a yarn engaging edge which extends through the entire thickness of the wall of the bobbin, so that the yarn engages the entire thickness and not the individual paper layers.