If two diagonals are given, then we can construct a:

The two diagonals of a rhombus bisect each other at 90 degrees. So, it can easily be constructed if the length of only two diagonals is given.

For eg:

Construction of a rhombus ABCD in which diagonal AC = 8 cm and diagonal BD = 6.2 cm.
 

• Draw line segment AC = 8 cm.
• Draw the perpendicular bisector of AC.
• With O as the center and radius = 3.1 cm, mark arcs on both sides of AC to intersect its perpendicular bisector. Mark the points of intersection as B and D.
• Join points A, D, points C, D, points C, B, and points B, A.
• Thus, ABCD is the required rhombus.