What is an eight penny nail?

Found at http://coe.fgcu.edu/bengel/Nails.htm





Origin of ';Penny-wise'; Nail Designations





There are two explanations for the English ';penny'; system of designating nails. One is that the eight-penny, six-penny, two-penny nails, etc. were so called originally because one hundred nails cost eightpence, sixpence, two pence, etc. The other theory says that one thousand eight-penny nails,


for example, weighed eight pounds, one thousand four penny nails weighed four pounds, etc.





The ';d'; abbreviation for penny, (8d for example,) is of ancient origin and represents the first letter of the Roman coin denarius.





Nails used with wood, (such as wood siding nails, cedar shingle nails, etc.), are traditionally referred to by the ';penny'; designation, i.e., as 5d or 6d nails, etc.. However, nails for non-wood applications, (fiber-cement siding nails, metal roofing nails, etc.) are primarily referred to by inches, i.e. as s1 1/2';, or 2'; nails, etc. In our literature, the penny designation is listed first for those nails that are usually referred to by that term.What is an eight penny nail?
the designation is 8d nail. stands for the size which is 2 1/2';





see http://www.sizes.com/tools/nails.htm