well, the seawall is 1863' long, since a foot has 12 inches that's 1863*12 inches, now if we divide that length by 18, because each clip is going to be 18" away from each other, that gives us

Now, let's think of each segment beginning with a clip, that makes it 1242 clips and since the seawall must end with a clip, that means 1242 + 1 = 1243 clips total.