take one ordinary plastic kitchen trash can, preferably the kind with a dome lid. the lid usually comes with a flap that slides up in the front so you can put trash in and the dome lid itself pops off so you can take trash out.
station your trash can next to a kitchen cabinet. make sure to turn the trash can so the flap opening faces the cabinet rather than into the room. now, head to you local hardware store. you'll need some sturdy wire and a tiny metal latch. the kind that looks like an upside down question mark works best to guard against critters without opposable thumbs.
attach the question mark part of the latch to the flap that opens, and the other half of the latch to the lid right below. the wire you'll want to run loosely around the trash can, attaching it on both sides to your kitchen cabinet. if you make the wire too tight you'll have trouble getting your trash can in & out when you need to. a way to make it a little safer it so hide the wire underneath the lip of the dome lid, where it attaches to the trash can.
congratulations you now have a berner proof & in our house an ultra intelligent cat proof trash can. as a bonus you also have an after dinner party game - see if your guests can figure out the puzzle. i haven't had one yet that could. ;)
laura & baka chapel hill, nc