Re: Line from the hardware store?
If you buy lines on eBay or other websites make sure that you know the size that you want. All lines but the mainsheet and jib sheets on your dinghy are probably 3/16" or maybe 1/4". Halyards sized for a keelboat will be way too big for most dinghies. On my 505 nothing larger than 1/4" (~6mm) would fit through the masthead sheaves, and 3/16" (~4.5mm) is the ideal size.
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior