Mr Ibrahim is testing the woodwork for strength, checking how well it has been assembled.
Joinery relies on precisely cutting and piecing together sections of wood, without using screws and brackets.
Cheaper, mass-produced imported furniture and declining incomes have mostly relegated joinery to a dying skill in the Levant.
In the region, the small industry's crisis has been compounded by the war in Syria in the last decade, which has cost the country a significant proportion of its artisans.
“Joinery still has its customers,” Mr Ibrahim says. “If these students end up with a few customers each it would be enough”.
One of the standard joinery techniques he teaches is called “the two lovers”. Another is known as the “dove’s tail”. While the technique names have a poetic ring, the workshop's atmosphere is professional.
The top three or four students can qualify to take courses in putting mother-of-pearl inlays into wood, wood carving and mosaics, which require even more precision.
The courses are run by Turquoise Mountain, a charity supervised by Prince Charles, who is due to visit Jordan this week with his wife, the Duchess of Cornwall.
The charity is helping preserve joinery and other crafts in the region, such as fine stonework, relying significantly on refugees from Syria to pass on their knowledge.
With help from the organisation, which also works in Myanmar and Saudi Arabia, Mr Ibrahim trained at a workshop in Jordan run by a master Syrian carpenter, who taught him the skill of making wood mosaics.
“For a long time, I only watched him. The craft taught me to be calmer, and more organised,” says Mr Ibrahim.
About half of the dozen or so students in the class in Amman are from Syria.
The country was renowned for inlay work and other crafts, such as textiles, before a 2011 revolt against the five decade rule of the Al Assad family and the ensuing civil war.
Prince Charles’ connections helped secure a spacious villa that became a training ground for the students. It is situated near the impoverished outskirts of Amman, where many of the apprentices live.
The white stone villa with a tower in the middle belonged to Sheikh Nasser Al Sabah, a late senior member of the Kuwaiti royal family, who was a patron of the arts.
Before he died last year, Sheikh Al Sabah lent the villa to Turquoise Mountain to use as a training centre.
The students train at an annex in the terraced garden. One is Musaab Al Saidi, who fled his home town of Homs in central Syria to Jordan when he was a boy in 2013. He studied engineering at a university in Zarqa, near Amman.
Restrictions on Syrian refugees make it difficult for Musaab to find blue collar work in Jordan.
He attended the joinery class after passing entry procedures to learn how to work with his hands, and possibly make an income.
“Even when I see two pieces of wood connected together it is an achievement,” Mr Musaab says.
Other students do not have a high school qualification. Some have been working odd jobs, usually in construction, before taking the course.
Hana Faouri, training manager at Turquoise Mountain, says the crafts being taught are “endangered” in the region.
“We are trying to reach a new generation of trainees, to learn these crafts and keep them going,” she says.
Prince Charles' trip to Jordan on Tuesday, and later to Egypt, aims to promote environmental and heritage preservation, as well as job creation.
The hilltop villa of the late Kuwaiti benefactor will be among his first ports of call.