Wine Glass Holder Can Anyone Explain What Cut A Perfect Line Through The Top Of A Wine Glass In My Cupboard?

Can anyone explain what cut a perfect line through the top of a wine glass in my cupboard? - wine glass holder

I have stories about my family a spider or some sort of insect that listen straight through the glass. Yesterday I found one of my wine glasses with a cut line on the dream of 1cm. From above. I was able to separate the ring without interruption! All other boats are available in the cupboard intact.How?