Sorry about the poor audio quality.
To do this trick, simply triple jump onto the slope on the side (any slope will work), and slide down head-first.
In the first section, this results in a hugely fast speed because the initial part of the dive is much faster than the rest of the dive. Since the height of the dive is so low, the dive is reset almost immediately, meaning Mario can keep travelling at the velocity of the fastest part of the dive.
In the second section, the long jumps are so high that a large amount of the level can be skipped. To do this, the trick is done in reverse.
One of these is likely to help for speedrunning the game.
Just used the mountain clip to break the previous record for Springboard Any% by 0.5s or so. Found it hard to get consistent and doesn't save too much time overall but good find and maybe more useful if made more reliable
