Notes

"Spellotape" is a play on words which is lost to Americans. Rowling is making a reference to Sellotape, a familiar brand in Britain.

Sellotape is "a British brand of transparent, cellulose-based, pressure-sensitive tape, and is the leading brand in the United Kingdom. Sellotape is generally used for joining, sealing, attaching, and mending." The name is used generically for household tape in the same way that "Scotch tape" is used in the US (Wikipedia).