Hi David,

I am assuming that this is one straight piece of railing as in the diagram.

d is the distance between the centre points of the first and last spindle and s is the distance between the centre points of adjacent spindles. Hence

d = 144 - 1 5/8 = 142 3/8 = 142.375 inches.

There re 17 spindles so there are 16 spaces between adjacent the spindles and thus

s = 142.375/16 = 8.8984375 inches.

Your tape measure probably is in sixteenths of an inch so

0.8984375 × 16 = 14.375

and hence the spacing between the centre points of adjacent spindles is approximately 8 7/8 inches.

Check:

16 × (8 7/8) + 1 5/8 = 16 × (71/8) + 13/8 = (1136 + 13)/8 = 143.625 inches.

Thus in the total length this spacing will leave you almost half an inch short and thus you will need to adjust the last few spindles slightly so that the spacing looks uniform.

Harley