When the tip of the needle tries to penetrate the fabric, it initially meets resistance and tries to push the fabric down into the opening of the needle plate. The bigger the opening, the more it is able to push the fabric. When the needle pulls back up, it then pulls the fabric back with it. This movement of the fabric can make it look like the tension is off. The position of the knot in the fabric will not be consistently in the middle. In extreme cases, it can cause skipped stitches. When you are sewing on very fine fabric or starting on a corner, it can also cause the fabric to be chewed up.The tiny hole in the straight stitch plate prevents the fabric from being pushed down and will give you better stitching. Of course, choice of needle also plays a role, but the right plate sure helps.
The thing to remember is that you will not be able to zig-zag or change needle position, or you will hear that crunching sound that means a broken needle. If you are fortunate enough to own a machine that lets you tell it what plate you are using, it's a feature to take advantage of.
Until next time, Bernie
