Sentence:  He stood a bit far of the gloom of the lobby, but short of the dazzle of the stairs, and he clenched his briefcase at his chest in a tense and <WSD>both-handed</WSD>, reptilian grip, as if whatever he had in it must be guarded at all costs. 
Meaning of the word marked with <WSD> tags:  For use with both hands or using both hands.