### Theory:

Draw a line $$MN$$ and mark a point $$P$$ above it. Through $$P$$ draw a line parallel to $$MN$$.
Step $$1$$: Draw a line $$MN$$.

Step $$2$$: Mark a point $$P$$ anywhere above the line $$MN$$.

Step $$3$$: Place the set square below the line $$MN$$in such a way that one of the arms that form a right angle lies along $$MN$$. Place the scale along the other arm of the set square.

Step $$4$$: Fix the scale stably. Glide the set square along the arm of the scale until the other edge of the set square reaches the point $$P$$.

Step $$5$$: Now draw a line through $$P$$ and extend it to $$Q$$.

Step $$6$$: The line $$PQ$$ is parallel to the line $$MN$$. That is, $$PQ \parallel MN$$.

Draw a line and mark a point $$S$$ at a distance of $$3.6 cm$$ above the line. Through $$S$$ draw a line parallel to the given line.
Step $$1$$: Draw a line $$XY$$.

Step $$2$$: Mark a point $$T$$ anywhere on the line $$XY$$.

Step $$3$$: Place the set square in such a way that the vertex of the right angle coincides with $$T$$ and one of the edges of right angle lies along $$XY$$. Mark the point $$S$$ such that $$ST = 3.6 cm$$.

Step $$5$$: Now draw a line through $$S$$ and extend it to $$R$$ using set square.

Step $$6$$: The line $$SR$$ is parallel to the line $$XY$$. That is, $$SR \parallel XY$$.

Draw a line segment $$PQ = 13 cm$$. Mark two points $$A$$, $$B$$ at a distance of $$4 cm$$ above the line segment $$PQ$$. Through $$A$$ and $$B$$ draw a line parallel to $$PQ$$.
Step $$1$$: Draw a line segment $$PQ =13 cm$$.

Step $$2$$: Mark two points $$X$$ and $$Y$$ on the line segment.

Step $$3$$: Place the set square above the line $$XY$$in such a way that one of the arms that form a right angle lies along $$XY$$ and coincide with the point $$A$$. Measure the length of $$4 cm$$ along the another arm and mark it as $$A$$.

Step $$4$$: Now move the set square along the line $$XY$$ until its vertex point coincide with $$Y$$.

Step $$5$$: Now draw a line through $$P$$ and extend it to $$Q$$. Again, measure the length of $$4 cm$$ along the another arm and mark that as $$B$$. Now joint the points $$A$$ and $$B$$ by drawing the line.

Step $$6$$: The line $$AB$$ is parallel to the line $$PQ$$. That is, $$AB \parallel PQ$$.