i am making a treasure chest cake and I wanted to know how to make it opened so I can put stuff coming out of it. I see so many pictures of them that, which I think is so cool.

You could prop it open with some skewers or dowels. I only had one skewer that I couldn't cut, so I had to hide the skewer as best I could with fondant and jewels. You can see the picture in my photos. I used RKT for the lid because I thought cake might be too heavy.