The idea of siting the vines in shallow trenches came from an internet article about grape growing in Moscow. But it was in use long before that, the Reverend Phillip LeBroq advocated growing vines in trenches (albeit very much wider and deeper) in 1692 to cope to cope with the temperatures of the Little Ice Age. The trenches then were covered with with oiled canvas when frost threatened. I aim to try that sometime, but up till now, 3mm twinwall poly carbonate has been used as covering. The vines are pruned to very short rods with canes (1-2ft in length) folded beneath the covers which are weighted down with stones, when frost threatens. The covered trenches act as a pit-greenhouse. Tests in February 2014 showed that temperatures could be maintained above 0 C in the trench with frost temperatures as low as as minus 7 C.
The logic behind the north-south alighnment of trenches was to maximise solar warming of the soil. In reality, I don't think it made much difference, and later trences were aligned east-west along the south-southwest facing slope. Various linings to the trenches were tried. Paving slabs as linings (lower left) seemed to cool the trenches on the often cloudy days. Wood lined trenches (above, with newly planted Jublienka Novgoroda vines in 2015) worked ok but eventially rotted. Unlined trenches were easy to make but prone to caving and weeds tended to grow in the walls.