TOAST

hi,
I an using postgresql-7.1beta4 and am trying to use the large text fields. 
I have heard of TOAST. There is little documentation. 
  I found one section about creating a data type,
then creating two functions to convert the data types.
Is this how TOAST is implemented?
Am I on the right track?.   If so,  what do
the conversion functions look like. I am using plpgsql.
Thanks, Pam