Hello candidate,

A network solid or a complete joining solid refers to a covalent compound which has a large number of covalent bonds mutually interacting with each other in the molecular form forming a case like or rig like structure holding the the element together in it's pure crystalline or amorphous form.

Here are some example of network solids- the structure of ice, the silicon dioxide atoms joining to form the complex structure of sand, are some of them.

Hope you found it helpful. If you have any further queries feel free to post it here!!