Tailing is an enzymatic method for adding a non-templated nucleotide to the 3' end of a blunt, double-stranded DNA molecule. Tailing is typically done to prepare a T-vector for use in TA cloning or to A-tail a PCR product produced by a high-fidelity polymerase (not Taq) for use in TA cloning. TA cloning is a rapid method of cloning PCR products that utilizes stabilization of the single-base extension (adenosine) produced by Taq polymerase by the complementary T (thymidine) of the T-vector prior to ligation and transformation. This technique does not utilize restriction enzymes and PCR products can be used directly without modification. Additionally, PCR primers do not need to be designed with restriction sites, making the process less complicated. One drawback is the method is non-directional, meaning the insert can go into the vector in both orientations.