Factory hold down. I cut off about 3/8 inch from the ends and cleaned the threads to prevent damage to any underlying electrical connections or wires.
Footnote, not meaning to hijack the thread or rain on your parade. I am a former Optima user. I have just returned three of then at less than two years for full refunds, because they gave out. I never had a problem with an Optima--and I used many over the years--until Johnson Controls moved their manufacturing to Mexico. Then like magic, my experience turned bad. Maybe it's the Arizona heat, and the Massachusetts cold won't be an issue. I have a $50 Checker-Schucks-Kragen battery of the same exact age that's going strong (in one of the PTs) but the the $150 Mexican Optima Red Top in the other PT gave out. I've replaced the Red Tops in my truck with Dekka yellow tops, made in the USA. Time will tell on those.
I hope your experience will vary and that I just got three bad ones. I really liked those Optimas!