The traditional formulation for random sequential adsorption (RSA) of line segments onto a plane does not possess a jamming limit; there is always space for a 1D object on a 2D plane. We propose a qualitatively different RSA formulation for line segments which does lead to a finite jamming limit, 1.5707 +/- 0.0001 segments per square one segment on the side. To our knowledge, this is the first appearance of the number pi in the jamming limit of an RSA problem. This RSA formulation can be applied to adsorption of rigid, very high aspect ratio rods on a flat surface. These rods are not well modeled by the traditional RSA formulation. As an example of such a problem we describe the deposition of carbon nanotube-DNA hybrids on a surface and show that our theoretical formulation is consistent with experimental results. (c) 2008 Elsevier Inc. All rights reserved.