[1] It is made of cast concrete, one piece of which is a prestressed concrete beam, which can be an inverted T-shaped beam, or lintel, the other piece being a simple rectangular block.
Propless systems used heavier inverted T beams to compensate for the exclusion of props.
The lintels and blocks are packed above load bearing walls under supervision and design by a structural engineer.
This system is extremely versatile in achieving complex designs and using unskilled labour.
From a structural viewpoint a lighter slab assists by allowing load-bearing walls and foundations to take less strain.