When you have multiple ad slots of the same size on a single page, you might want to control which creative serves to which ad slot. For example, if you have a series of 300x250-pixel ad slots running down the side of the page, you might want to put a particular creative first, second, and third.
To get the right result, you can use a combination of roadblocks and incremental ad unit sizes.
Set up ad units with incremental sizes
To control the order of creatives, set up ad units that have both their actual sizes and incrementally bigger sizes. For example, for the three sequential 300x250-pixel ad slots, set up the following ad units and sizes:
Ad unit 1: 300x250
Ad unit 2: 300x250, 300x251
Ad unit 3: 300x250, 300x252
Notice that each ad unit has its actual size, and the sequentially placed ad units also include an incrementally larger size. By including both sizes, you set up the ad units so that they can receive both sequential and non-sequential creatives.
Traffic line items to the sequential ad units
If you're not concerned about the sequence of the creatives that are delivered from a particular line item, traffic everything normally. However, when you want to control the sequence:
Add all of the sequential sizes to the line item. (In this example, the sizes would be 300x250, 300x251, and 300x252.)
As an alternative, you can use a master/companion roadblock. Enter the first size as the master, and enter the incremental sizes as the companion sizes.
In the Adjust delivery section, change the option for Display creatives to All. (If you're using a master/companion roadblock, set Dsplay companions to All).
Add the sequential creatives. For each creative, set the Target ad unit size to the incremental size of the ad unit to which it should serve. You can still use a creative asset of the basic size. For example, Ad Manager will deliver a 300x250 image file from a creative that is targeted to a 300x252 ad unit size.
Define the ad slot sizes
To serve sequential creatives correctly on a single page, you need to define the ad slot sizes in your tags. This section explains how to do so with the Google Publisher Tag (GPT).
For the first ad slot, use the normal size:
For the second and subsequent ad slots, include the incremental sizes:
Notice that the name of the div for each ad slot is different, which is a requirement.