´It was narrated from 'Amir bin Sa'd that when Sa'd was dying he said:` "Make a niche for me in the side of the grave and set up (bricks) over me as was done for the Messenger of Allah."
Hadith Referenceسنن نسائي / كتاب الجنائز / 2010
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم
Urdu marginal note: "To place bricks" means to close the mouth of the lahd (side niche in the grave). And this is an inexpensive method, whereas covering a shaqq (trench-type grave) is costly.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 2010