1 Land contracts or contracts for deed are a security agreement between a seller, called a Vendor, and a buyer, called a Vendee.  The Vendor agrees to sell a property by financing the purchase for the Vendee.
The two DNA strands are held together by interchain hydrogen bonds. H-bonds pair the bases in one chain to the complementary bases in the other chain. (A/T and G/C).
A DNA strand is simply a string of nucleotides joined together. I can show how this happens perfectly well by going back to a simpler diagram and not worrying about the structure of the bases. The phosphate group on one nucleotide links to the 3' carbon atom on the sugar of another one.