I have about 3m of dado trunking in my office (brand unknown) providing sockets and phone points which my electrician brother-in-law fitted about 15 years ago. Sadly he has passed away and I now want to shorten the trunking at one end to push a tall cupboard back against the wall. I can see that the top and bottom trims are pressed on at the wall edge and hinged at the centre edge but how do I remove the front covers. There are no screws holding the sockets in place. I know that the supply comes through the wall somewhere along the trunking but can't find out where yet.