XF 1.4 Nodes Choice for Ad Display

Hi - I'm struggling abit..

I have been searching for an example of placing ads using the template hooks ad_ with the conditional statement of a given node. For example what statement should I add to the hook to only show the ad within a given node or nodes.

Appreciate any advice.
Many thanks - I've been searching the Forum off and on for about 2 hours - and you gave me the answer within a few minutes.
Much appreciated!