ALT + 0151 is called ascii code. Where in one of the ascii code for the "space" is 0151. In where Jagex didn't allow players to type ascii codes in their chat log, in which ascii wasn't enable in their Java.
Like in exampe, the ascii code for ® is 02222 and ™ is 0153.
In where if you use it in an auto type, it will register the space ascii and would do the space if you hit the code. But some keyboard's has some special characters ready.
I had to use auto type before to play pranks with noob in typing special characters in RS.
Nice guide. Not useful but good for playing pranks.