Create a Lookup column from a list in a separate web

Problem:  I have a site collection (SPSite) with multiple sites (SPWeb) and I have a reference list in the SPSite (root web) that I want to use from multiple lists in the sites (SPWeb).

Resolution:  I recorded this short video that shows how to create a lookup site column in the site collection and then at the list within a sub web, you can associate the lookup.