Sticking Edge of MDF Board to a Tiled Wall - What's Best to use? Advice and information on tiling and fixing tiles to a variety of surfaces

[Zacccc]

Can anyone advise on the best stuff to use to stick the edge of an MDF off-cut to tiles?

I've got a bit of a mess of pipes running behind the toilet so I've covered them up by boxing them in using some off-cuts from old MDF kitchen units. I've got the boxing all done but it leans slightly towards the toilet from the tiled wall behind the toilet, leaving a gap of about 7mm between the wall and the edge of the MDF unit that is the 'top' of the boxing. I want to stick this MDF edge to the tiled wall.

[Theinsulationshop]

'Fix all' by soudal works really well and comes in a range of colours. It's not a silicone either but you still can't paint over it, but once it dries it's brilliant