Lesson Notes By Weeks and Term v4 - JHS 2

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Identify tools for measuring and marking out.
• Describe the purpose of each tool.
• Understand why accurate measurement is important.

Lesson summary

In Ghana, from the seamstress in Makola Market creating a beautiful dress to the carpenter in Anloga building strong furniture, and the mason constructing a new house in our community, success depends on one crucial first step: measuring and marking out accurately. This topic is the foundation of all technical and vocational skills. If your measurements are wrong, your final product will be wrong, wasting time, materials, and money. The popular saying "measure twice, cut once" is the heart of this lesson. Today, we will learn to identify the basic tools that help us achieve this precision in our work.

Lesson notes

Before we look at the tools, let's understand two key terms: Measuring: This is the process of finding the size, length, width, height, or quantity of something. We use standard units like millimetres (mm), centimetres (cm), metres (m), inches (in), and feet (ft). Marking Out: This is the process of transferring measurements onto a piece of material (like wood, metal, or fabric) to show where to cut, fold, drill, or join. The marks act as a guide.

We can group the tools into two main categories, although some tools can do both jobs. A. Measuring Tools

These tools are primarily used to determine dimensions. Steel Rule: Description: A flat, rigid ruler made of steel. It has very clear and accurate markings, usually in both metric (mm, cm) and imperial (inches) units. Main Use: For taking precise linear measurements on flat surfaces. It is more durable and accurate than a plastic ruler for workshop use. Example: A student in a workshop uses a 30cm steel rule to measure the length of a small piece of wood for a key holder project. Tape Measure (Measuring Tape): Description: A long, flexible strip of plastic, cloth, or metal marked with measurements. It is stored in a case and can be retracted (pulled back in). Main Use: For measuring long distances and curved surfaces. Its flexibility makes it very versatile. Example: A carpenter measuring the dimensions of a room to build a wardrobe, or a tailor measuring a client's waist for a pair of trousers. Folding Rule: Description: A ruler made of several sections connected by pivot joints, which can be folded together. It is usually made of wood or plastic and is very rigid when extended. Main Use: Commonly used by masons and carpenters for general measurements. Its rigidity allows it to be extended into the air without bending, which is useful for vertical measurements. Example: A mason checking the height of a wall he is building. B. Marking Out Tools

These tools are used to draw lines and points on materials. Try Square: Description: An L-shaped tool with a thick wooden or metal part called the "stock" and a thinner metal blade. Main Use: Used for two main jobs: (1) Marking lines at exactly 90 degrees (a right angle) to an edge. (2) Checking if a corner is "square" (a perfect 90-degree angle). It is a measuring *and* marking out tool. Example: A carpenter uses a try square to draw a straight line across a piece of wood before sawing it, ensuring the cut will be perfectly square. Marking Knife: Description: A very sharp, knife-like tool with a bevelled edge. Main Use: Used to score or cut a very fine, precise line on wood. This line is much more accurate than a pencil line and provides a starting groove for a saw or chisel. Example: A cabinet maker marking out a joint on a piece of Odum wood. Scriber: Description: A tool with a sharp steel point, similar to a pen but for metal. Main Use: Used to scratch or "scribe" fine lines onto metal surfaces for marking out. A pencil mark would rub off metal easily, but a scribed line is permanent. Example: A metalworker marking the position for a hole to be drilled on a sheet of metal. Centre Punch: Description: A small, hard steel rod with a sharp, conical (cone-shaped) point. Main Use: Used to make a small dent or "punch mark" in a piece of metal. This mark serves as a guide for a drill bit, preventing it from slipping or "wandering" when starting to drill a hole. Example: An auto mechanic uses a centre punch to mark the exact spot on a metal bracket before drilling a hole for a bolt. Tailor's Chalk: Description: A small, flat piece of hard chalk, often in the shape of a thin triangle or rectangle. It comes in various colours (white, blue, yellow, pink). Main Use: Used to mark lines on fabric for cutting and sewing. The chalk marks are easily brushed off and do not stain the cloth. Example: A seamstress marking the pattern outline on a piece of Ankara fabric before cutting it to make a dress. Marking Gauge: Description: A wooden or metal tool with a stock, a stem, and a sharp pin or "spur" at the end. The stock can be moved along the stem and locked in place. Main Use: Used to scribe a line that is perfectly parallel to the edge of a piece of wood. Example: A carpenter marking a consistent line along the length of a wooden plank to show how wide it should be cut. Dividers: Description: Looks like a drawing compass but has two sharp steel points instead of one point and a pencil. Main Use: Used to scribe circles or arcs on wood or metal. It can also be used to "step off" or transfer a measurement multiple times along a line. Example: A craftsman marking out a circular pattern on a piece of calabash for decoration.

Evaluation guide

• B8.3.1.1
• Demonstrate understanding
• of measuring and marking
• out tools and equipment