He has to, as the man deals with millimetres, literally.
A crossbow champion, Brewer knows all too well what the result is if he is off by the slightest margin.
''Consistency in what you do with it, be one with the machine and be very still,'' Brewer said when asked what makes a good crossbow archer.
''I think one of the boys did a little thing and for one millimetre out with the sights on the shooting line at 50m I'm 100mm off target.
''So it has to be absolutely dead still.
''If you can slow your heartbeat down, that's good; you can shoot between your heartbeats.
''You can see it in your sight, so as soon as that sight's still, you let the shot go.''
It is something the Dunedin clockmaker has become very good at since taking the sport up 12 years ago.
He has about 15 New Zealand records and won the 2015 national championships.
Held over five days, the championships are a cut-throat event in which one shot can be the difference.
''Ninety-six bolts [shots] a day,'' he said.
''You just don't take the eye off the game. One shot can cost you the whole thing. It's the tension I like; I thrive on the tension.''
He had hoped to go to world championships, although his health had prevented him.
That has not knocked him though and he has had taken the season off competition to experiment with things.
However, he is hoping to get back into it and win the national championships again next season in order to qualify for the world championships.
It was a long way from when the father of two got into archery when his son, Alex, began.
''All archers are like that.
''Most adult archers you find their children join, the father joins, the child leaves and the father stays on.
''I used to be a smallbore rifle shooter and I was very good at that.
''When my boy got old enough to go shooting I thought archery would be a good thing.
''So we came down and learned together in the class and went from there.''
It has become a huge passion.
He has done a lot with customising his equipment so it best suits him and he enjoys the relaxation you get from the crossbow.
The president of the Dunedin Archery Club for the past four years, he has plenty to do with the sport on the administration and coaching level too.
There are about 30 learners in the city, who train on a Saturday morning, while another eight seniors train in the afternoon.
While he is not wanting to carry on in the role for a fifth term, he has got much enjoyment out of it.
''It's great to see when the kids learn to shoot.
''They come out on to the field here and they shoot for badges for different distances and they hand out badges.
''You get to know the kids and stuff. It's absolutely brilliant, so it has a lot of pluses.''
