[Term in DART for Publishers] Roadblock Contains two or more linked ads that serve together on the same page. Each roadblock must contain one master ad and can contain up to six companion ads.
Roadblock Serves creatives from a line item (ad in DFP) together on the same page. Roadblocks in the new DFP are set up in a single line item that contains all of the creatives for the roadblock. Roadblocks are set up in a line item's settings in the 'Deliver Creatives' drop-down list. Learn more about roadblocking creatives