How does the Space Shuttles arm work in space without leverage?

Call this a dumb question, but after thinking about what just happened with the Hubble Telescope and pulling it into the Shuttles bay for repair. My question is this: if I grab a chair and pull on it, my weight offsets the weight of the chair and allows, with the help of my shoes and the traction to the ground created by friction, me to pull the chair, but only to the point that my legs or shows give way mainly due to the weight. So, being weightless in space, when the space shuttle arm pulls on the Hubble to relocate it to the inside of the shuttle, how does it attain leverage to create movement without leverage? Doesn't it require weight or m to create leverage? Thanks-