Portal - Stuck on lvl 19

[dss]

Im really enjoying Portal, but I'm stuck at this one bit.. really frustrating!

Its the place with the sort of sewage system and then loads of Sentrys come out of those rooms, Ive killed all the sentrys but im stuck as where to go next! Any hints appreciated

thanks,
dominic

 

[dss]

Wow, fast replys

thanks ill try it now

edit: got up, thanks for the hint