between each nucleotide? It's confusing

Can you understand "a section of double-stranded DNA between each nucleotide ?

Context:

The second problem, Gundlach said, was that the nucleotides flowed through the nanopore at a rate of one every millionth of a second, far too fast to sort out the signal from each DNA molecule. To compensate, the researchers attached a section of double-stranded DNA between each nucleotide they wanted to measure. The second strand would briefly catch on the edge of the nanopore, halting the flow of DNA long enough for the single nucleotide to be held within the nanopore DNA reader. After a few milliseconds, the double-stranded section would separate and the DNA flow continued until another double strand was encountered, allowing the next nucleotide to be read.