You use them on one project and then you can't use that item again on something else, like a sticker or a brad or anything else consumable - an embellishment rather than a tool.
LOL, no I know what "one time use" means, I just can't for the life of me figure out if the OP thinks that the wood shapes are dies or some other sort of tool of if she's talking about something else all together. I wanted more info. I realize now that it looked like I was asking you!
I have used wooden and chipboard shapes like that as masks before using them as embellishments, so I'm not sure exactly what the OP means by the one time use - as some embellishments like that can have more than one use (masks, embossing, sanding guide, etc).