When you manhandle something, you pick it up, push it, or pull it roughly. You might gasp watching movers manhandle your fragile furniture as they load it into a moving van.
You can manhandle things, and you can also manhandle people, shoving or grabbing them. If security workers at the airport manhandle a little old lady, nearby passengers will probably speak up in her defense. This current meaning arose in the late nineteenth century — earlier, manhandle meant "attack an enemy," and before that, "wield a tool."