Interesting 2019 report on the Mk-Alg smuggling scene.

It’s well know that in the 80s the Moroccans pushed up a huge, 2000-km fortified and mined sand wall or berm (left and right) between their part of the Western Sahara and the remains of  the Polisario-controlled lands to the east. It stretches from the Atlantic border with Mauritania northeast towards Smara, on the way cheekily chopping off the desolate corner of Mauritania (not shown on all maps). After Smara it then runs up towards Zag until it reaches the natural barrier of the Jebel Ouarkaziz ridge – the southernmost outlier of the Atlas mountains – right around here and just 22 miles from southern Morocco’s N12 highway.

The periodic foums and oums (natural gaps in the ridge) sometimes become locations for strategic forts or installations, like the abandoned one at KM227 on Route MW1 in Morocco (above) from the Polisario war.

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It seems the Algerians have got the same idea and have been building an intermittent berm of their own along exposed sections of their border with Morocco where foums in the Ouarkaziz or later, Jebel Bani, would have allowed easy motorised passage.

Click on this point in Algeria some 40km southeast of Mhamid in Morocco, and you can follow the zig-zagging berm northeast for some 40km via a small erg, until it stops near a ridge where rough terrain resumes the job. Branch berms break off to make enclosures or to complicate scouting along the main berm for a gap, and every once in a while there’s some sort of installation, fort or look-out post pushed up by the bulldozer. They even incorporated little gaps for the oueds to flow though (above right) and which are quite possibly mined. Any passages through the small erg are also blocked with a berm (below right).

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Way further east towards Figuig, a gap in the jebel there demarking the Moroccan border where the old Oran–Colomb-Bechar rail line used to run has been bermed too (above left).

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Nearby, just to the south in Algeria is a monument to General Leclerc whose plane crashed near here in 1947 – it’s pictured on a commemorative stamp. Among other heroic wartime deeds, he’s famed for leading an armoured column up though Chad to help the LRDG attack the Axis forces based in Murzuk, Libya. There are many more monuments to the WW2 liberator of Paris in North Africa and France.

Reading the article linked at the top of the page and it becomes clear traffic flows both ways over the long-closed border. Algeria claims Morocco smuggles loads of hashish southwards to befoul it populace, or to get it to European markets via other routes.
You imagine a berm is fairly easy to make once you order a conscript with a D6 to get on with it.
There’s been bad blood with Morocco for as long as the two countries have existed. Despite Morocco’s wishes, the border with Algeria has been closed to all since the mid-1990s.

More berm activity way down south at Bordj Moktar