Different parts of the country use various installation methods which may or may not be included in the TCNA Handbook. While it is best to follow an established and proven method, some installation methods that are not in the Handbook do function without problems. Spot bonding tile, however, is not one of them.
Spot bonding either floor or wall tile calls for a glob of mortar to be placed on the back of the tile and spread around with a margin trowel. Most times there is no attempt to key the mortar into the back of the tile, which results in a questionable mechanical bond. The tile is then placed onto a dry, unclean, un-mortared substrate which does not encourage any type of mechanical bond to this surface either. Needless to say, almost every industry-recognized recommendation for the proper installation of tile is compromised with this technique.