To draw a line segment through a point T, parallel to line PQ. There are two set-squares in your geometry box.
Take one of the set-square and place its edge along PQ as shown in the figure 1.
Place the other set-square along the first set-square as shown in the figure 2.
Now, slide the first set-square until its edge comes to pass through the given point T.
Draw the line RS passing through the point T as shown in the figure 3.