To deploy them, you grab a handle and pull a lanyard that goes to the pin holding the container closed. The pilot chute is also attached to the lanyard. The action of pulling the handle out to the side first opens the container and then pulls the pilot chute out to the side. Pull Out versus Throw Out Skydivers who use throw outs tend to disparage pull outs, and vice versa. With a pull out, the container is still closed if the handle is dislodged.
Nothing comes out unless the handle is pulled.
Pull out partisans argue that you don't need to worry about being inadvertently deployed if your handle is knocked loose. With a throw out, if the handle is dislodged, the pilot chute is out and deployment begins. People preferring pull outs also say that you are unlikely to have a pilot chute in tow situation, because you, not the pilot chute, extract the pin. Finally, unlike a belly band or leg mounted pilot chute, you can't misroute the bridle and there is no bridle outside of the container to snag on things or blow loose in the wind. A remarkable number of reserve rides, and quite a few fatalities, have resulted from this situation.