Spring mode
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  When you click with the mouse, if there is a mass nearby, one end of
a spring is connected to it.  The other end of the spring is connected
to the  cursor until  the  mouse button  is released.   If no mass  is
nearby when the spring is  released, the spring is discarded.  The new
spring takes on the values of the "Kspr" and "Kdmp" gadgets.  The rest
length of the spring is equal to the length of the spring when  it was
created.

 - Left mouse button  adds a  spring between two masses while actively
affecting the first mass.

 - Middle mouse button (*) adds  a  spring  between the first mass and
the  cursor,  actively  affecting  the  first  mass.   The  spring  is
discarded when the mouse button is released.

 - Right mouse button  adds a spring between two  masses.   The  first
mass is not affected by the  spring until the spring is in place after
the mouse is released.

  Please read the  Window Activaton help page concerning
middle and right mouse button clicks.

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  (*) Users of two button mice may simulate the middle mouse button by
pressing  the  left or right mouse button while holding down any 'alt'
key.