UI corner dissapearing from side to side

So basically I’ve been trying for a long time to make Frames with UICorners in it or even UIStrokes to slowly dissapear from one side to another like this.
robloxapp-20220711-2356330.wmv (247.6 KB)
So far all my attempts were pretty much useless. Had to recreate this topic because my old one was inactive. I hope I can get some feedback.
I asked my friend how he did it and he told me something about up and down position. I didn’t understand.