In many levels, at the end, you can switch your weapon to the bow in order to save fractions of a second.

This happens because the code that checks for finishing the level is: "if x-position > 235 or (the bow is selected and x-position > 230)"

So if you change your weapon to the bow right before finishing the level, you can finish the level 5 pixels earlier, which may save 0.1 seconds in ILs. One example of this is in the level Training Level, which is a level you can beat just by holding right. If you hold right without switching to a bow, you get 0.6 seconds. If you switch to a bow last second, you can get 0.5 seconds.

This doesn't seem to fully save 0.1 seconds(maybe around 0.05 seconds, but I'm guessing on that), so sometimes switching will do nothing. One example of this is in the level Test, where you get 2.3 seconds regardless of what weapon you are holding.

Also remember not to switch too early because if you hit a wall/ledge on your way to the end with the bow, you will lose your 5 pixel advantage.