Are carpenters trained to use levels or do most just not care?

Oh I care.  You put the thing on a surface and measure the bubble. 

There.  I have trained you.  Now get a job.

A good carpenter will use a level, Jesus wouldn't be caught without one, he was one of the best carpenters. 

This post was edited by TomThumb at December 16, 2016 2:21 PM MST

Carpenters sleep with a level. ;)

They are and should! Squares, too

My first home was built in about 1850, and consisted essentially of a rectangular box of semi-random stone walls divided internally by woodwork. Investigating my difficulty in trying to lay square-cut hardboard on the worn-out bathroom floorboards, I found the room was out-of-square by as much as 6 inches in only 6 feet length of wall: an error of 1-in-12, or nearly 5º!

Most people know how to use a level.  what most people don't know is how to take care of and calibrate their levels or which type and size is best for the task.

Thank you Evil Pink Bunny. I wondered about settlement given the nature of the hillside on which the village sits, but there was no sign of it in the walls. I think houses like that were built with little regard for accuracy, because that was simply not needed at the time. They were careful to make the walls plumb and the floors level, but squareness of partitions was not so important.

I once felt something odd about the stairs in a restaurant in my town's sea-front, late-18C terrace. Weymouth (the English one) is built on a bay-bar of clay, so one might expect some sinking but all it seems pretty solid and I've not heard of any subsidence problems in its buildings. Even so, those stairs didn't feel right, and I realised they had subsided slightly to one side. The angle was very low but enough to be noticeable in walking up and down them.

Calibrating spirit-levels. Yes, It's caught me out! I was puzzled why despite every care to lay the bricks level to a string or even a straight-edge screwed to posts, the mortar joints in the garden wall I was raising were tapering steadily down from correct thickness until I was almost having to just brush it on at the other end. Then it occurred to me to test the level. Sure enough, it was out by about 1/8" over its 3-foot length.

I'd long wondered how builders coped before the spirit-level was invented, then by chance saw a Mediaeval wood-cut of masons at work. It showed them testing for level by using a large square with a plumb-line on one edge.