Tiling the underside of boxing

[Rusti]

Hi,
I need to tile the underside and side of some boxing on the ceiling but whereas on the walls I've been able to fix batons and set the tile positions with spacers and wedges, there is no support on the boxing to set them against. I am thinking I could screw wood in place on the bottom of the box to support the side ones, but I can't think of a good way to support the bottom ones properly. Has anyone any experience of this sort of thing?
Thanks

 

[PrenticeBoyofDerry]

If the tile are heavy a wooden prop can be used, if they not so heavy some anti-slip adhesive will hold them, or you can use gaffer tape or combination of both.