The driveway and garage door are on the opposite side of the house to the wall where you placed the red line on your thumbnail, koios.
If this was a random opportunistic abduction, I'm not sure someone was necessarily inside the garage, but moving around the house where the figure of the child is (again, on your thumbnail).
I have always been very suspicious that the grey sedan William's Mum remembered she had seen parked across the road when she opened the curtains first thing that morning. Also, the grey-green sedan that drove past the house, and did a u-turn at the dead end, at around 9 am (when the children were riding their bikes on the driveway).
I suspect they were one and the same car. It just seemed to be two cars of 'different' colours to William's Mum but only because the colour 'changed' depending on whether she saw it in the sun or the shade.
http://www.portnews.com.au/story/33...ice-seek-information-on-two-cars-audio-video/
Photo:
https://en.m.wikipedia.org/wiki/Disappearance_of_William_Tyrrell
If you look at this photo from Google Earth:
There is a clearing with a space large enough to drive, and conceal, a car off the road between No's 48 and 30 Benaroon Drive.
The bushes and that side of the house would have given good cover for a person, so it would've just been a matter of the perpetrator quietly moving around that side of the house, where he could hear the family and William's Dad's plans to leave, etc.
When William's Dad left, the opportunity to abduct a child presented itself. The perpetrator could have moved his car into the clearing, or simply moved it onto the same side of the road, as soon as William's Dad turned out of the street.
It would've taken seconds for William to be grabbed, bundled into a car and for the perpetrator to quietly drive away from the house. William's Mum wouldn't have heard a thing as she was inside, at the opposite side of the house. The perpetrator would have been out of there before anyone knew William was missing.
