At my company:
Inteviewer: So you are a carpenter?
Carpenter: Yes.
Inteviewer: Can you make a start fixing that leaky roof over there? We will monitor your skills and might hire you.
Carpenter: Done.
Inteviewer: So you are a carpenter?
Carpenter: Yes.
Inteviewer: Can you make a start fixing that leaky roof over there? We will monitor your skills and might hire you.
Carpenter: Done.
The only problem I've seen with this approach is where the applicant is legitimately pressured for time by their current work or family issues. Being understanding and working out how to extend the trial period will get you through most of these.
In countries (like mine) that don't have at-will employment it amazes me that employers don't insist on this approach. Instead - weird filtering by recruiters, overly specific interview questions and then disappointment when recruiting goals aren't being met and stress when developers who aren't a good fit are stuck with the team for years.
You will not hire anyone currently employed like this. You would be unlikely even to hire a contractor.
Carpenter: I'm breaking your roof.
John: Yes?
Interviewer: Can you fix the roof by tomorrow? This interviewee that was supposed to fix it really fucked it up..
John: But.. I've got to make this architectural blueprint for... sigh fine.