Steps of construction:
1. Draw a line segment $BC=6cm$.
2. Then, draw perpendicular with the help of scale, $AD=8cm$ to BC.
3. With A as a center and radius $5cm$, draw two arcs with the help of compass , on both sides of line AC.
4. With C as a center and radius $5cm$, draw another two arcs with the help of compass, cutting the previous arcs at B and D both side.
5. Now Join AB, AD, BC and CD.