The Vietnamese word "dây mực" refers to a "chalk line," which is a tool used in construction and carpentry. It is a thin string coated with chalk powder. When you pull the string tight and snap it against a surface, it leaves a straight line of chalk, which helps you draw straight lines for measuring or marking.
In more advanced contexts, "dây mực" can also refer to precision in measurements, emphasizing the importance of accuracy in construction or artistic endeavors.
While primarily it refers to a chalk line, in some contexts, "mực" alone can mean ink or squid, depending on the usage. However, when combined with "dây," it specifically indicates the tool used in marking.