互

hu

mutual, reciprocal

each other

picture of two hooks hooking each other;

Roofing tiles are made in such a way that they mutually compatible

瓦

wa

tile (crijep, pločica)

earthenware (zemljano posuđe)

When the shape of two tiles fitting together “互[hù]” came to mean ‘mutual,’ the Chinese added a dot (丶) to stress the meaning ‘tile.’

a curved interlocking roof tiles

瓶

ping

bottle, vase, flask

combine (bing) + tile (wa)

to combine fire + clay to make a ceramic vase or bottle

并

bing

to combine, merge

to unite,

side by side; also

a simplified form of 並, two men 竝 standing

Two people (丷) standing side by side (丨丨) under one roof (一) = (merged) 并 (united)