From your description it sounds like you're playing the "Catch The Dog" sequence. Here's the
walkthrough image (from our
walkthrough archive).
There are several topics about this episode in the
Machinarium Puzzle Q&A section ( try searching for "dog" ).
The other advice I'll give you is: Look closely at the walkthrough image and keep in mind that when Europeans write the number "7" they add a stroke through it to distinguish it from the number "1".