Lucas Samaras

Lucas Samaras was another artist that used boxes to do artwork.
The picture above is one of the boxes that he created that i liked the most.
The box clearly has shards of glass sticking out of it, but i'm curious about the texture of the rest of the box. Is it sharp all the way around? Is that yarn or electrical cords at the top of the box? Why does the box open at the top if the inside is covered by that metallic shiny plate? It is an interesting box indeed.