kel med 2 skifter, 2 spær, trimpel og stol

Danish to English Other Construction / Civil Engineering Svendebrev for Tømrerfaget

The context for the phrase is: "Svendeprøven er aflagt i tømrerfaget bestående i at udføre Kel med 2 skifter, 2 spær, trimpel og stol ..."

I have: The apprenticeship exam was undertaken in carpentry and consisted of the completion of a valley with two _____, two rafters, a ridge, and a timber cradle.

Not the most elegant, but it's a first draft. I'm struggling with the English equivalent of "skifter." The two definitions I have that may or may not be related to the "skifter" in the phrase above include: skifte = vandret lag af mursten or skiftespær = spær, der går fra tagfod til grat, eller fra kip til kehl (kehl=kel). Both of these definitions are from: http://www.danskbyggeskik.dk/dictionary/Ordbog_klar.pdf

I'm not terribly confident I have the right English terms for the phrase. Any advice on better or more commonly used terms in North American, but particularly Canadian, English would be much appreciated!
Thanks in advance!