A fine film. This tells the real story - with the inclusion of one of the actual protagonists - of the planning of an escape from jail of four long-term prisoners; and how when a fifth prisoner is brought into their cell - who they are naturally uncertain about - potentially changes their plan.
The way the escape is done shows the sheer monotony, graft and hurried patience needed to execute such a plan. We see a heck of a lot of digging, more than most other films would show, almost bringing us in as one of the escapee's urging us to help shift the dirt away quicker. The lead (real-life) escapist Roland is just amazing, he is very adaptable, knows everything about escaping, thinks on his feet to come up with quick solutions to problems, and is almost machine-like in his digging; he is naturally muscular and has a look of a guy who would snap your neck without hesitation and remorse if you got on the wrong side of him. In one scene, as he's making a tool, you could see a stub of a thumb where you imagine what scenario that happened to him. He was a multiple escapist and there is an interview with him on Youtube where he tells us some of his past criminal life and how it honed his escape skills.
The strange but brilliant thing the director does, is not bother us with the past stories of the four long-termer's, but instead tells us the backstory on the fifth guy Gaspard, who is almost aristocratic in nature, who doesn't really deserve to be there and has a coming trial for attempted murder of his wife where there is a real possibility of him getting out; and you can see there are times when he clearly is thinking only about himself, whilst the others are thinking about the group. This leads to tension between them and it builds as the film progresses.
Its shot in a matter-of-fact way, without fat as we only focus on the group and not prison life; no music (great!); and the execution of the escape. It might be just a tad long, but it is very watchable indeed once you are involved.
I like this a lot too, and quite a bit of what I wrote about Le Samourai applies here also, I think. There is something about the French crime film of this vintage (and perhaps the novels from which most of them derive, I dunno). The preoccupation with graft, as you say. The obsessive focus on minutia, practicalities, professionalism, craft, capability, repetition and incremental progress. Bresson is the obvious touchstone again, but all the best ones from the 50s and 60s have something of it about them... Rififi, Grisbi, Classe tous Risques, the earlier Melvilles, even some of the more routine Grangiers and Verneuil... criminality as a skilled trade, with codes and mores.
A lot of them focus on the physicality of that, on the hands specifically, but this is an exceptionally tactile sort of a picture even by those standards; a film of callouses, and dirt under the nails (which marks laddo out as the black sheep from the start, I guess). There's a realism in that, but then something more too, a heightened realism. The pleasures of observing that craft, the moments of quiet grace therein, and the moments when that spareness/stillness/tension is punctured by something else (on which note the sound design of this film is tremendous in that respect). All especially emphasised here because we are told so little about the characters. There's no question of morality about any of it, or any of them (until the end perhaps, and even then it's an austere and oblique sort of a judgement). Just their actions, their being, their being together.
Aside: On the evidence of this and La Grande Illusion banged up Frenchmen ate really fuckin well, dint they? Wouldn't mind some of those care packages.