Japanese changing rooms

I went to try on a dress in a department store in Tokyo today, and the sales assistant gesticulated for me to remove my shoes. She then pointed at a circular piece of cloth with a lace loop/hanger, which was hanging on a hook in the room. Any idea what it was, and what it's for? Also, is there any changing room etiquette I need to know in Japan? What would be the correct thing to say when you want to try something on?

You have to remove your shoes when using changing rooms in Japan and leave them outside of the room.

Kyi,

Isn't that the "hood" you are supposed to put on to avoid leaving makeup stains on the clothes you are trying on?

What would be the correct thing to say when you want to try something on?

"Shichaku shite ii desu ka?" (Can I try this on?)

In some shops, they also forbid to try on T-shirt, dresses, and other things that you have to pass your heads through to put on...
Don't know why...

Tatum,

That would be at shops where they do not provide those "hood" or face cover sheets to avoid makeup staining the shirt you're trying on.