Smaller hook and eyes are used on garments to prevent gaps such as at the tiop of a zipper. The zipper rarely goes to the very edge of the garment because it would be unsightly and uncomfortable. By adding a hook and eye closure above a zipper, you can keep the same seam line and prevent a gap at the top of the zipper. In some cases, such as a tight fitting garment, the hook and eye may help to hold the garment closed while other closures such as a zipper, are being closed.
A purchased hook and eye does not mean that you need to use both parts. In many cases a thread arrangement is used for the eye rather than the metal counterpart. The thread arrangement tends to lay smoother and is less conspicuous.
Color choices of Hook and eyes are very limited. Black and silver is usually the only available option. Use silver for light color fabric and black for dark fabric.
Pointers for Sewing a Hook and Eye