If you live in the country near a river or forest you will probably have rats nearby. When the weather turns cold they want to come inside your house or barn where it is cosy.
There are a lot of Instructables for trapping rodents but if you have more than one or two, trapping is really not a satisfactory option. This bait station is easily made from two plastic milk bottles and keeps the bait away from pets and birds.

Step 1: Tools

Common tools needed are a hammer, needle nose pliers, box cutter, and utility scissors.
Several sizes of nails and heavy staples are also used.

Step 2: Materials

Two one liter or quart plastic milk containers, a heavy block of wood a little longer than the milk containers.

First:
Cut the end off of both milk bottles and remove caps. The rats can enter through the top or bottom.
Cut a square hole in one, leaving about 25mm (1 inch) at the bottom end. Remove the cap. This will be the bottom.

Step 3: Attach Container to the Wood.

Using a pair of needle nose pliers to hold the staple in place, hammer it through the bottle into the block of wood. Use three or four staples to ensure the bottle stays attached. The block of wood keeps the rats from taking the bait and hording it. The objective is to kill the rats, not give them a storehouse of bait.

Step 4: The Top

Cut the handle end off the other container, try to leave it as long as possible. Cut a strip off one length but leave "wings" to hold the top onto the bottom.

Step 5: Baits

These are three of the brands of bait available in New Zealand. It's a good idea to give them more than one kind so they don't develop immunity to one or if they're picky eaters.

Step 6: Fix Baits

Many brands of bait have holes in them. Nail the bait through the plastic into the wood. Rats love to take the bait away, you want the bait to stay where you put it. Sometimes when I get up in the morning the rats have moved the whole bait station, heavy block and all, several meters. At least the baits are still attached.

Step 7: Slide on Top

The top fits over the opening in the bottom container. This keeps the weather out and also prevents pets and birds from eating the bait. The hole can be cut shorter, rats can get into very small spaces.

Step 8: The Finished Bait Station

The top slides off to attach more bait. Pick the whole bait station up by the handle. Make sure you wash your hands thoroughly after handling any poison or wear gloves.
You could camouflage the station with leaves or wood but I like to see at a glance if I need to refill it.