Sentence:  I seized the rack and made a western style flying mount just in time , <WSD>one</WSD> of my knees mercifully landing on my duffel bag - and merely wrecking my camera , I was to discover later - my other knee landing on the slivery truck floor boards and - but this is no medical report . 
Meaning of the word marked with <WSD> tags:  having the indivisible character of a unit