many to many bi-direction table relationship

Gavin McMurdo

To the Wise Ones 

I’m looking for guidance on how best to handle relationships between two tables with the goal of the lowest read latencies possible. I have a rental tools table and the store locations table. Each of these tables contains the details specific to the store and the tool. I would like to have a relationship between the two that is bidirectional and many to many. 

What are the best practices to implement something like this where there can be many of those tools in many locations. I would like the lookup efficiency for the tool locations and the list of tools at a location to be efficient and high performance.  

I hope my question is making sense.

Thanks in advance