Installing a shower cubicle

I believe the glass (which has no cavity) should be masticed on the inside [and outside if you want]. The metalwork forming the channels within which the glass is held at the wall should be mastic'ed on the outside [and the inside vertical edges if you want] but the inside bottom edge of the channel should be left clear.

Thanks By the bottom edge I assume you mean the edge in contact with the shower tray

You are correct.

Coincidentally, we have just had one fitted, and the water ran along the bottom metal channel and out at the corner. And it is quite difficult to get a mastic gun under the door and down the channel, but I think I've bunged it up for now.

You win!

I followed the instructions for my Bathstore enclosure. Silicone only on the outside.

The previous houseowner installed a shower enclosure and used silicone on the inside. If you didn't keep the silicone clean and dry, it started to get a coating of mould. The instructions which came with my new (Aqualux) shower, suggest silicone on the outside of the enclosure, where the glass comes into contact with the tray. I'll be using silicone on the outsde only. Bertie

The instructions on the one I've just fitted say seal on the inside of the vertical joint at the wall, but outside only along the bottom edge to the tray.

I have just re-fit our ensuite and sealed both the inside and the outside of the shower enclosure. However, this seemed to be leak free but a couple of weeks later it started to leak from a corner. I think water was building up somewhere inside the frame and reaching a level where it would then leak out. I ended up removing some of the interior silicone around each corner to allow the water to escape back into the tray. If I ever fit one again I will silicone the outisde only.