Hello and thanks for using Just Answer.
I am Al and am happy to assist you with your enquiry.
To be 100% safe, a simple Licence agreement should be drawn up. This sets out ehat right you are granting your neighbour, but as it is a Licence, it means either party can terminate the agreement (and hence the right granted) by giving the other party at any time. A Solicitor can prepare this for you, and would prevent yor neighbour from acquiring any permanent right, which could be transferred to any subsequent owner of the property.
If you did noot want to go to the expense of using a Solicitor, you could draw up a simple Licence Agreement yourself.
All it needs to include is your full names and addresses.
What right is granted.
A sentence confirming- "the parties agree that this is a Licence and can be terminated by either party at any time, by giving the other party written notice"
Then the agreement needs to be signed by you bot and dated.
I hope this assists and sets out the legal position.