How can i make a peice of a bread bag into a hard peice of plastic?

Question

You know those flimsy plastic bread bags that you can get, well i need it to be hard so it can be a little wall in my terrarium to hold up a lot of dirt...

Answer 1

Can't quite figure out what you're trying to do,  Could you take a picture of this terrarium?, Or explain further.

Answer 2

please please please please answer my question :)

and do what the question ask you to do