stacking two matrices



hi community,

doing some linear algebra, I want to stack matrices one below the other 
to get a new 'stacked' matrix. I tried buildin functions like append etc 
but I was not clever enough .. maybe you can help me. 

A:matrix([1,2],[3,4]) 
B:matrix([5,6])

A and B stacked should give:   matrix([1,2],[3,4],[5,6]) 


A somewhat general wish is to insert a matrix ('row') at a special position:

A: matrix([1,2],[3,4]) 

insert B:matrix([5,6]) as row 2 in A should result in: 

matrix([1,2],[5,6],[3,4]) 

Any hints are welcome.

HTH  Wolfgang