Joan,  a  rather  well-proportioned &  near-sighted secretary, spent
almost all of her vacation sunbathing on the roof of her hotel.  
She wore a bathing suit the first few days, but always removed her 
glasses for an even facial tan.  After several days she decided that 
no one could see her way up  there, so she slipped out of her suit 
for an overall tan.  She'd hardly begun  when she heard someone running 
up the stairs; she was lying  on her stomach, so she just pulled a towel 
over her rear.
"Excuse me, miss," said the flustered little assistant manager of the
hotel, out of breath from running up the stairs.  
"The hotel doesn't mind your sunbathing on the roof, but we would very 
much appreciate your wearing a bathing suit as you have for the past
week." 
"What difference does it make?" Joan asked rather calmly.  "No one
can see me up here, and besides, I'm covered with a towel."
"Not  exactly," said the embarrassed little man. "You're lying on the
dining room skylight!"