A string of beads can resist longitudinal force (force along the string) in two ways. Let's have the string of beads vertical, so as to demonstrate how they can resist gravity... Without either method, the string of beads will fall over once let go at the top. Not something our tai chi mastering beads would wish to do... ;-) First, the "external" method: draw the string that holds the beads together taught against the ground, so as to hold the beads tight against one another with tension. Now the top can be let go of, and the beads will stand up, due to friction and tension. Simple, but wastes energy. Additionally, the ground is not in perfect contact, necessarily, and if one were to add to the force of gravity by pressing down at the top, eventually the friction and tension would be overcome and the structure would slip (a little or a lot) and the ground resistance/power/inertia would not be transferred to the top bead. Second, the "internal" method: from the vertical position, take care to balance each bead on top of the next. If done correctly, the string is not used, and the beads will stand upright once the last bead is in place. Simple, but takes lots of skill. Once mastered, the beads stand upright with no effort and resist the force (gravity in this case) simply due to the alignment and structure of their parts. Thus, the ground is in perfect contact, and all resistance/power/inertia of the ground transfers completely through the structure to the point of contact (top of the bead tower in this case). [at least until one of the beads crushes under the pressure... ;-) ] If the beads are smart and skillful, then one can apply force from all sorts of directions and the beads can "re-balance" and set up another effortless ground power transfer. Additionally, if the beads had some muscle, then they could store and release power along this path and effortlessly resist the equal-and-opposite-reaction effect, effectively doubling the power and keeping their stability. And this is exactly what one does with an internal martial arts strike, via store-and-release. Sound reasonable? What I like to tell people real fast is that setting up the peng path is kind of like balancing two staffs end-to-end in the palm of your hand - once you get it right, you can feel it, and any pressure applied to the top of the top staff gets transferred perfectly down to your hand. Then I show them how to do it. Structure, dynamics, and intent. Or so it seems to me.