I'm sure you know that you should be very careful using a trolley jack on carpet!
The trolley should be free to move so that as the point of lift moves backwards (as the arm swings up) the trolley tends to want to move forward to stay directly under the weight. If the car cannot move and the jack is snagged on the carpet it could be dangerous!
Bottle jacks and scissor jacks just raise directly upwards, a trolley jack swings backwards on its arm as it is raised.
