You can find a list of all default keyboard shortcuts at http://www.inkscape.org/doc/keys046.html -- unfortunately it doesn't include one for locking an object. But there is a keyboard definition for Illustrator CS2 users. You can read how to change your keys here at http://tavmjong.free.fr/INKSCAP...

Hello, Im an Adobe Illustrator User who is considering switching to Inkscape permanently... im currently evaluating what inkscape can offer over illustrator... I have to say that the things I hate about illustrator (gradient tools, no cloning and no transparent color as gradient color are OK in inks...