to this end , therefore , i will not say 'the one in the window is the last one we have , and we ca n't sell it to you , because if we did no one would know we have them for sale ' , or 'we 'll probably have some more on wednesday ' , or 'we just ca n't keep them on the shelves ' , or 'i 'm fed up with telling people there 's no demand for them ' i will make a sale by any means short of physical violence , because without one i am a waste of space .