On the number line, create a right angle triangle with a base of 1 unit and a height of 2 units. The hypotenuse length is square root of 5.
Using a compass, draw a circle using the point on the triangle where the base and hypotenuse meet as the center, and the point where the hypotenuse and height meet as to draw the circle. The point where the circle and number line intersect is where sqaure root of 5 is.sqaure root of 5 lies somewhere between 2 and 3. 
Initially draw a line with 1 unit difference and mark as XY
now mar A at 0
from point 2 draw a perpendicular and mark B at 2
now with 1 unit measurement draw an arc on perpendicular line and mark as C
join A and C
now using compass join C and XY