The horizontal tasting is conducted by focusing on a wine varietal from a single year, but from multiple producers. Basically you grab a 2005 Cab from 4-6 unique wineries and give them a go side by side.
For example, you may want to pick a Cabernet Sauvignon as your varietal and compare Napa Valley Cabs from 2005. So you might try the 2005 Clos Du Val Napa Valley Cabernet Sauvignon, the 2005 75 Wine Company Cabernet Sauvignon and the 2005 Carpe Diem Cabernet Sauvignon and so on.
Some of the variables to consider here are whether or not you would like all of the wines to be from the same region. You can shake it up and feature a Cab from Washington, Chile, California and Australia from 2005 or consider limiting it to all Napa Valley Cabs from 2005. It’s your choice.