<h5 style="color: rgb(51, 51, 51);"><font color="#000000"><span style="font-weight: bold; font-family: Arial, sans-serif;">Hollow block</span><span style="font-family: Arial, sans-serif;"> is a special kind of machine-made </span><span style="font-family: Arial, sans-serif;">hollow block</span><span style="font-family: Arial, sans-serif;"> with a locking mechanism in its structure which helps form linkage between blocks.</span></font></h5>