Perpendicular Through a Point on a Line

When you need a right angle at a specific point on a line, this construction gives you a clean, reliable perpendicular without any measurement. It is used for margins, page frameworks, and alignment systems.

By drawing a circle centred on the chosen point, you create two equal distances along the line. Those equal distances become the centres for arcs that define the perpendicular.

Step‑by‑Step Construction

• T draw a perpendicular line through a point on the line A-B
• Place the compass point on the chosen point C.
• Draw a small circle that cuts the line at two points (D and E).
• From D and E, draw arcs of equal radius so they cross above or below the line.
• Connect the crossing point (F) to P.
• This line is perpendicular at P.