Alot of gardeners will use the insides of loo rolls to sow long rooted plants such as peas and beans. I have a huge number to plant this year, and once I knew this, I started collecting them [last summer].
I started to get quite a collection, so I had to work out how to store them otherwise Mark would be chucking the whole lot out when we ran out of space.
So, I have been folding them and storing them as shown:
This means, once they come out, they can be used as squares, rather than as rolls:
They can then be used to split square pots as such:
This gives you 4 separate areas within one pot.
Or, as below, where you can have 9 different areas within one pot