Direction
Use pam-Grid-Control="direction:[row|row-reverse|column|column-reverse]"
to control the direction of the grid.
Column 1
    Column 1
    Column 1
    Markup
<div pam-Grid pam-Grid-Control="direction:column">
    <div pam-Unit="1-3">
        <div pam-Unit-Test>Column 1</div>
    </div>
    <div pam-Unit="1-3">
        <div pam-Unit-Test>Column 1</div>
    </div>
    <div pam-Unit="1-3">
        <div pam-Unit-Test>Column 1</div>
    </div>
</div>