Looking up for a moment from sorting through a mountain of blue and green plastic bottles, Mounir throws to one side a clear plastic container.
Some of the detritus of 16 million people is brought to Moqattam
Although the plastic has already been meticulously pored over by his wife and daughters, one "stray" has managed to slip through.
His deft hand movement ensures it lands where it belongs - among the clear plastic.
Mounir's family are zabaleen (rubbish collectors) living where life's left-overs in the great metropolis of Cairo end up.
Here the detritus from many of Cairo's 16 million inhabitants is carefully sorted, compressed, washed, resold, reworked, or simply used again.
Moqattam is the largest zabaleen settlement, home to about 30,000 recyclers. It sits in a quarry on the far side of the Moqattam hill, so is invisible from the city.
Everything thrown away in Cairo, every newspaper, torn pair of trousers or slice of bread, starts on a secret journey from the moment it is put in the bin.
It is not a trail of chaos - but of professionalism, ingenuity and imagination, crystallising into an industry as efficient as it is unknown.
The zabaleen are one of a number of autonomous groups that keep the city clear of rubbish while at the same time making a living.
Traditionally the main division is between the zabaleen and the wahiya (oasis people).
The latter came around 1900 and took on responsibility for household waste disposal, selling it as fuel either to heat the public baths or for cooking.
Moqattam has grown into a major settlement behind Cairo's citadel
The arrival of the zabaleen about 50 years later from villages in Upper Egypt pushed the wahiya up a notch.
Now the wahiya are middlemen, acquiring the rights to service buildings and selling collection routes to the zabaleen.
Zabaleen make money from feeding the organic waste (about two-thirds of the total) to their livestock and recycling the rest.
The women of the household sort out the various categories - plastics, glass, metal, paper and textiles. It's hard work - but more environmentally friendly than the mechanised garbage crushing trucks from Europe that the municipality brought in about 10 years ago.
Once rubbish has been mechanically compressed, no recycling is possible. It can only be dumped.
Mounir's wife Layla empties bags on the floor for her four daughters to rummage through. She sees her job as vital for the city's survival.
"We don't like attention. Rubbish is never attractive and we're quite happy carrying on quietly... but our work supports a whole industry that's virtually invisible to most people."
Nor is Layla's daughter ashamed of her life.
Bags of rubbish are stored in the street ready for processing
"The people employed by the city just pick up rubbish because they are paid to. For us it's different. It's in our blood," she says.
These are people who grow up with the notion that just because something is thrown away it doesn't mean that's the end of its life.
Specially designed machinery recycles different plastics, turning them into black bags. Rags are washed and woven into bags and bright carpet squares.
The new generation of zabaleen are likely to have been to college or university, and are turning their hand to electronics recycling.
Computers, laptops, adding machines, mobile phones, and answering machines are all finding their way up to Moqattam.
Dia, one of the new generation of entrepreneurs, explains that, as Egyptian society evolves, the ingenuity of the zabaleen is stretched to keep pace with what's being produced.
"We're in a transitional phase. We have huge quantities of tins that are brought up here every day. Every time an Egyptian has a soft drink from a can, he is creating work for us".
"People still think of us as just collectors, but really we are doing Cairo a huge service... We have some basic industries now - all started by our own experience."