I remember about 6 years ago I took a masters ski course and one of the coaches was talking about the purpose of cross-blocking. He said that cross-blocking is a function of body position. If you watch closely in world cup slalom skiing, you will notice many different styles of cross-blocking. Some skiers reach out and place their pole in front of their face to cross-block and some keep the arms low and touch at the same time they "boot" the gate. The style of cross-block may depend on the particular style the skier uses when they approach a SL course. One thing they all have in common, which differs a little from master's skiing, is speed. Many of the world cup skiers ski very fast through an SL course as compared to masters racers. Speed facilitates cross-blocking because of the amount of lateral movement required to complete a turn on SL skiis at a high speed.
Cross-blocking becomes natural because in SL you ski fairly close to the gates, however it is not always fast, especially in masters racing. I remember when I first learned to cross-block. I started out making the same mistakes every master's racer makes when they are first learning. I would reach out across my body with my outside hand to brush the gate out of the way. This mistake is simply corrected by starting your turn earlier and skiing a little closer to the gates. After about a season, I finally got the line right and cross-blocking became easy. The funny thing was that when I entered my first SL race at the end of that season, my race time wasn't all that fast. Even though, I cross blocked every gate perfectly and made all the gates easily, I didn't have a fast time. Another strange thing, was that there were a couple of racers who beat my time, who just skied around the gates and didn't touch them at all. I thought this was really interesting because skiing a wider line should be slower in theory. So why is this? Recently I have been taking the time to watch other master's racers ski through SL gates. Most cross-block. Some even have the technique down so well that every turn seems set up so perfectly that the cross-block looks so natural. However again, it isn't all that fast. When you watch world cup SL, very few of the racers look like they are skiing in control. And the ones that do look like they are in control, usually don't win the race. This is not the case when you watch masters. Most look like they are skiing completely in control, every turn set up perfectly, every cross-block easy. Which is great if you are trying to look good and save yourself from losing teeth. But if you ski an SL race like that, you might as well stay home. I stopped trying to cross-block a year ago. Now, I just raise my hands and touch the gate wherever it happens to be. Sometimes I brush it with my inside hand, sometimes with the bar on my helmet, sometimes with both hands, sometimes with the inside shoulder and sometimes I cross-block (outside hand). What I don't do is compromise my speed, my body position, or turn shape in order to set myself up for the perfect cross block. For me this approach is always faster. When I do cross-block, it usually means my line and timing just happened to be accurate for that turn. It's a consequence of good tactics. Although, I do have to wear a lot of protection, with this approach. (arm guards, shin guards, pole guards, thigh padding and my personal favorite: lacrosse gloves) Some day I am sure that my timing will be accurate enough that I will be able to cross-block every gate. But right now, I am more concerned with speed. I often take my first run or two to ski classic. I saw this done on a world cup training video once, and wasn't sure why they did it, but now I understand. It is to get a sense of the rhythm of the course at speed, so the speed doesn't end up getting sacrificed for cross-blocking. The series of photos below show examples of cross-blocking at different speeds, compare the body positions of these four master's racers with the world cup SL photo above on the right.