What do you mean by double armor and double knives?

For example, some people have a little knowledge, but they are not rich in knowledge. They only have a little skill, but their skills are not so strong. They refer to people with insufficient knowledge and low skills in a certain job. Also known as "two knives", "two knives in half a bottle of vinegar" or "half a bucket of water".

Two knives come from masons. Bricklayers only work in summer and autumn, stay at home in winter and spring, and supply and sell radishes in their spare time. So masons have the ability to carve radish flowers, cut bricks in summer and cut radish in winter, so they are called "two knives".

Another way of saying it, people call the bricklayer with the best technology "the head knife", and the head knife often stands in the corner, which is called "crib". The technology is not good enough, and it is barely called "two knives".