We've found a multitude of ways to break sail slides and consider ourselves quite adept at it. These are small T-shaped parts that are used to attach the main sail to the mast. On Nine of Cups, we use stainless steel sail slides at the high stress points and nylon sail slides at the intermediate points, and it is the nylon sail slides that break. We tried using all stainless sail slides, but found they were more prone to jamming than the nylon type, and we prefer to repair the odd broken sail slide to having a sail slide jam when we are in a hurry to get the main down.
They rarely break when the wind is strong. They are much more likely to break in light winds when the roll of the boat makes the main sail flog from side to side. When we are sailing downwind, we use a preventer to keep the boom from jibing, but the sail will sometimes try to jibe if the seas are running, and this often results in two or three broken sail slides. The lower slides are more prone to break, which is good, because they are easier to replace.
We never set out without plenty of spares, and we've had enough practice that it now takes only minutes to replace a sail slide. While we have replaced several while at sea, we can usually reef the main enough to postpone the repair if conditions are bad or if we will be arriving in an anchorage soon.
Take a look at a video clip we made that shows how we replace a sail slide.