take your plastic bottle and cut the top off as shown above.
cut down the removed section so that you have just the bottle neck.
place the neck inside the bottle. Add tape around the edge to hold together, and cover sharp edges. You could use coloured tape for this, we only had parcel tape so had to make do.
put in a teaspoon of food colouring, this colours the rain and helps it easier for small people to see/measure.
place you rain catcher in the garden, and close your eyes for every picture until Mum gives up and just uses any of them.
After it rains come and have a look and you should have something like this in the bottom of your rain catcher. We measured the rain 24 hours roughly after putting the catcher outside and have caught a whopping 12mm of rain in that time. Don't forget to fill any readings onto your weather chart!