If you are not familiar with the 2-prong fastener, it may help to think of it as a staple, which pierces the fabric and the bottom of the button. In a closed top button, the legs of the fastener then encounter a metal slug that has been assembled into the button. This slug has a curved bottom, which causes the legs to curl inwards and grip the button.

During application of an open top button, a die is inserted into the the button through the hole in the top of the button (the open top). This die causes the legs to curl and grip the button, much as the slug did in the case of a closed top button. After application, the die is withdrawn. This leaves the curled legs visible at the bottom of the button.

For an enhanced open top look, we have created a special version, available in 22 ligne and 27 ligne sizes, that has an inserted stamped slug which lies over the legs. This leaves a smooth rounded surface at the bottom of the cavity.

These designs can also be made using a single tack collet. However, nylon collets can not be used for open top buttons.