Adding a default binding to a keymap

[Lennart Borgman]

You can add a default binding to a keymap if you know the structure for 
a keymap. For example to add 'ignore you can do something like this:

   (setcdr (cdr my-keymap) (cons (cons t 'ignore ) (cdr (cdr 
my-keymap)) )) 

However it does not feel quite right. Is there another way to do this?