High explosive powder is shaken into the nose cone of an improvised missile through a funnel fashioned from a mineral water bottle.
One spark, a drift of cigarette ash, and the detonation of this arms factory would be heard and seen for many, many miles.
For more than two years the rebels fighting Bashar al Assad had been begging the outside world for help.
The US has recently decided to send lethal aid to the rebels - not game-changing equipment such as anti-aircraft weapons or tank-killing missiles - just small arms and rocket-propelled grenades.
Syrian rebels elsewhere have said today that they recently received unspecified new weapons and more were expected.
FSA spokesman Louay Muqdad said: "We've received quantities of new types of weapons, including some that we asked for and that we believe will change the course of the battle on the ground.
"We have begun distributing them on the front lines, they will be in the hands of professional officers and FSA fighters," he said.
The US is reluctant to send more powerful equipment because of fears that it could find its way into the hands of al Qaeda-affiliated groups which could then use anti-aircraft missiles to shoot down civilian aircraft.
Prime Minister David Cameron supports arming those rebels with no affiliations to al Qaeda - but whether he can sell the idea to Parliament remains in question.
Many British MPs do not believe that their national interests would be served by backing rebels who may turn against Europe.
But there remains another, more subtle, problem.
The self-taught engineers were making a remote-controlled rocket launcher out of plastic drainage pipes, the working parts of an adjustable TV satellite receiver and an old starter motor.
That level of artisanal arms manufacturing may, one day, pose a threat to the outside world from people who were abandoned by it.
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