If you like retro computing or have a computer from the 80s, you probably need this.

I hate to put a tape in that hole so my MSX can read HD disks as DD (High Density as Double Density), it's just ugly.
So if you are like me, this is for you. I prepared a printed cover that works with Maxell, Verbatim, KAO, Nashua, 3M, and Sony.
 
How to use it:
Put the floppy disk on top of the little block, align it with the hole, and apply some pressure with your hand on top of the hole.

Advice:
I did this to replace the tape on my disks. Use it at your own risk.
HD disks formatted with DD drives aren't guaranteed to lose data, but they're not guaranteed to keep it either. So if those HD disks were written at some point with a DD drive using the hole-cover, the bits might fade away. Maybe tomorrow. Maybe in 3 years. Maybe never.