An open sandwich is another way of tasting a sandwich. For general sandwiches, the stuffing is put between two breads. When tasting these sandwiches, we just take them with our hands to our mouth, and we taste them without any tableware. Different from general sandwiches, the stuffing of open sandwiches is put on a single bread. If we want to taste them in the way of tasting general sandwiches, it would not be convenient for us to do that, so we need a knife to cut a piece off and put it to our mouth with a fork. Open sandwiches could be seen in Europe nations. If you have a chance to have a tour there, you could give them a try.
Postscript: The picture is downloaded from the following website:
https://parade.com/842277/communitytable/open-faced-sandwiches-spicy-catfish-poboy/