The pruning article doesn't tell how to distinguish between new wood and old wood when pruning. I have 4 grapevines trained to an overhead trellis via 4 corner posts. Lots of small vines "crawling" and hanging on to of the trellis. We are expecting some 40 degree weather the next couple of days before daytime highs in the 20s set in the next week, so would like to prune the next couple of days.
Old wood are vines that is 2 years old, as these vines will no longer produce fruit.
When you prune in winter you remove almost all of the canes that are 1 year old and older, keeping only the canes that produced the previous season.
Trim the end of the remaining vines up to the stem size of a pencil, anything smaller will not produce fruit.