The basilisk gateway, was: Preparing

[constancevigilance]

Responding to my own post, but I had an idea that might answer both our 
questions.

Kneasy:
Who carved the serpent on the tap in Myrtle's bathroom and why?

CV previously: Furthermore, why was Tommy in the girl's loo anyway? 

CV: Perhaps Merope opened the chamber and carved the handle? She could 
speak to the basilisk, would have been in the girl's loo and could have 
left a trail for young Tom to follow somehow? Maybe there was something 
in the locket? Does the carving match the snake on the locket? It would 
be typical of an adolescent girl to decorate something with a personal 
mark. 

(Given our new image of Sally at JKR's website, does it seem a bit odd 
that he would be wearing a locket? It looks so uncharacteristically 
gentle for the rest of him.)