You will see a step between the dirt floor where you put your footwear and the floor inside at the entrance. The crossbar that is horizontally passed over this step is called Agarikamachi. Also, you will find that Japanese houses have few strict partitions and walls. However, there is a culture in Japan that gives names to the parts that separate these spaces and is clearly aware of the partitions.
For this reason, the crossbars on the up stile are also symbolically good. Since it is a space where many people come and go, durable wood is selected.