Step 1: Understanding the Concept:
The question describes a multi-purpose workshop tool used for checking flatness, marking parallel lines, and, most importantly, marking and checking 90-degree angles. We need to identify which of the given tools performs all these functions.
Step 2: Detailed Explanation:
Let's analyze the use of each instrument:
(A) Straight edge: A straight edge is a tool with a precisely straight edge. Its primary function is to test for flatness (by seeing if light passes under it when placed on a surface) and to be used as a guide for drawing straight lines. It cannot be used to check right angles by itself.
(B) Try square: A try square consists of two main parts: a thick stock (handle) and a thinner blade, fixed at an exact 90-degree angle to each other. It is a highly versatile tool:
Testing right angles: Its primary purpose is to check if an edge or corner is a true right angle (90°).
Marking right angles: It is used to mark lines perpendicular to an edge.
Testing flatness: The edge of the blade is a straight edge, so it can be used to check for the flatness of a surface.
Marking parallel lines: By sliding the stock along a true edge of a workpiece and holding a pencil at a certain point on the blade, a line parallel to that edge can be marked.
This tool performs all the functions mentioned in the question.
(C) Mortise gauge: This is a special type of marking gauge with two adjustable pins. It is used specifically for marking two parallel lines simultaneously, for laying out the boundaries of a mortise or tenon joint in woodworking. It cannot be used to test for flatness or right angles.
(D) Calipers: These are instruments used for measuring distances, such as the diameter of an object or the distance between two points. They are not used for testing flatness or angles.
Step 3: Final Answer:
The try square is the instrument used for testing flatness, marking parallel lines, and marking/testing right angles. Therefore, option (B) is the correct answer.