Hand luggage is rarely measured and even less often weighed. It does happen and some airlines are very strict but the majority of airlines only weigh checked luggage.
Before boarding most flights, there is a sizer close to the gate. It is a metal contraption that has the dimensions close to the maximum size allowed for hand luggage. Usually there are two parts to it, one if to measure the Carry-on and one for the smaller personal item. Most airlines in the world allow both but some only one which is another question all-together.
People godo not systematically use the sizer. Instead, the airline announces a few minutes before people board that the sizer can be used to check. When the flight is particularly full, they often walk around the waiting area and tell people whose bags seem very close or over the limit to check the sizer. A bag that fits within the sizer is let in, one that does not is checked. If you can squeeze it in, you are good.
Sometimes you are told that the flight is very full and there is not even room for all the allowed size for everyone. In which case, they offer to gate-check the luggage which is free of charge.
The bottom line is that weight is rarely checked and size seldom but the closer you are to the limit, the more chances you are of being checked. Most airlines are not bothered by being over by less than a kilo, but some are stricter. Westjet from experience is not so strict and I have never seen them weighing hand-luggage.