#31: Come On In, and Watch Your Step
This one seems bizarre on the surface, but it is, in fact, a very important custom among Buddhists. If you ever visited a Buddhist monastery, for example, you would have a similar expectation that you would not step on the threshold. The reasons for it are varied, but it is an old tradition.
The explanation is the threshold is something of a barrier. One version explains that getting it dirty would harm its ability to keep the building clean and ward away evil. Another possible reason is that it is seen as a barrier to the gods, will destroy your feng shui, and will clash with the family god.