Any ideas what these are for

So after a bumpy ride across 4 miles of lake, the following day while cleaning the boat I found some screws that had come loose from a speaker grill and also these. I can't find where they belong but they look important. I'm thinking they may be for the Bimini. Can anyone identify these:
https://uploads.tapatalk-cdn.com/202...dff2fd5203.jpg
They are solid stainless steel. Look like they plug something. Any thoughts? One was found under the helm area, another in the mid sitting area. That's why I'm thinking from Bimini. They look like they might be stoppers, but where from?


Sent from my iPhone using Tapatalk