The trailer is quite narrow and fits between the Pontoons. The Trailer actually lifts the deck of the Boat and does not support the Pontoons and the wheel base is quite small. This style of pontoon boat trailer can be retrieved and launched in the shallowest of water, since the Pontoons are very low to the ground.
Tanking is, as its name suggest a method of sealing a wall to prevent water ingress (think 'water tank). often mis-specified as a cure for damp problems it is basically a waterproof cementious slurry (wet mix) that is applied to a surface to prevent water penetrating the internal surface of a building..
The tank of a wall-mounted toilet is inside the wall behind it, so it uses the depth of the wall to reduce how far it protrudes into the room. For the carrier system inside the wall, you can get one that either fits into a wall with 2-by-6-inch studs or one that recesses into a wall with standard 2-by-4 studs. This is an example of a contemporary bathroom in New York.