Theory:

There are many places where we are see the perpendicular lines and parallel lines in our real life.
 
Just check out the following collage.
 
45badf9bf2262efb8adc8952e0ad0886_collage_450.jpg
 
Let us discuss the perpendicular cases:
  • The sides of the soccer field with the centre lines
  • Television screen with its edges
  • Some grills in the window design
  • Railway track crossing
  • Sign of the first aid kit
Let us check the definition of perpendicular line with an example:
Two different lines intersecting each other at right angle or \(90°\) are called perpendicular lines.
stock-vector-perpendicular-line-meet-at-degree-illustration-402381289.jpg
 
Let us check some more examples:
 
45badf9bf2262efb8adc8952e0ad0886_collage1_450.jpg
 
Let us discuss some of the parallel cases:
  • Lines in the race field
  • Railway track
  • Cars in the queue
  • Steel rack shelves
  • Sides of the road
Two lines are parallel when they do not intersect each other at any point on the plane. 
parallel lines-w1278.png
Set Square:
Two triangular instruments in the geometry box are called as 'Set square'.
  • Both the set squares has right angles in it.
  • One of the set squares is an isosceles triangle with two angles measuring \(45°\) on the equal sides.
  • Other set square is a scalene triangle with two angle measuring \(30°\) and \(60°\).
stock-vector-triangle-ruler-square-set-plastic-school-drafting-drawing-right-angle-triangle-ruler-plastic-1552389098.jpg
 
Uses of Set square:
  • To construct the specific angles \(90°\), \(45°\), \(30°\) and \(60°\).
  • To draw parallel and perpendicular lines.
  • To measure the height.