"Scare friends and family when you walk towards them as Life-Size terrifying Monster Robot. This amazing Robot obeys your commands."
Spoiler alert: it's made of fiberboard:
Actually I am flabbergasted that the ad would actually show how the whole thing looked with you inside, shuffling around in a big refrigerator box, instead of drawing a fantastical super articulated robot with laser rays, in a style similar to the missile firing tank from Honor House Products.
Also interesting is that this ad sells only plans for the creation of such a monster robot, as though you couldn't just figure it out from the image provided. At least missile-firing tank was actually a big pile of fiberboard and rubber bands that arrived at your doorstep with (I assume) instructions. To get your robot you actually have to go and buy your own robot parts.
But at the very least you can be rest assured that your satisfaction is guaranteed, because you are ordering from none other than... GUARANTEE COMPANY.
From Amazing Spider-Man #140, January 1975.