What marking is typically used to indicate the location of holes to be drilled?

The correct marking used to indicate the location of holes to be drilled is a hash mark. This is because, in aerospace assembly and mechanical drawing practices, hash marks are commonly utilized to denote specific points for drilling operations. They provide clear and unambiguous guidance for where the tool should be applied, ensuring precision in the assembly process.

The hash mark helps differentiate between various types of markings used on drawings, as it visually signals that an action is required at that location. A dot, while it can indicate points, is often used for other purposes such as reference points or centers, and may not clearly convey that a drilling action is needed. Similarly, an X mark is generally used to indicate areas that require inspection or are not to be drilled, while a circle is often associated with outlines of holes already present rather than locations for new drilling. Thus, the use of a hash mark is a standard practice in marking drill locations and facilitates clear communication and execution of assembly tasks in aerospace mechanics.