Overflow pipe.
Randy, I noticed in your picture that you have the overflow/drain already set in place. Then are you just dropping in the tub? Im no expert, but in all the books I have seen they show that this is installed on the tub, then the tub abd drain are all dropped into place. Your way seems a bit easier for restricted spaces. Is this how you did this? Im curious because I will have to do this in the next week or so, and this seems like a good alternative. Any drawbacks to doing it this way? Also, I see you have plasic under the mortar, Is this to keep the wood from drying out the mortar? So I guess the mortar doesnt bond to the floor, but just supports the tub? I have a Kohler tub with feet and they say to use mortar bed. Should I also use adhesive under the four feet? The tub doesnt have a nailing flange.