The Tao is an empty vessel; it is used but never filled.
Oh unfathomable source of the ten thousand things!
Blunt the sharpness,
Untangle the knot,
Soften the glare,
Merge with dust.
Oh, hidden deep but ever present! 
I do not know from whence it comes.
It is the forefather of the emperors.
 Lau has 'Let your wheels move only along old ruts'. The Ma wang tui text has '(It) settles the dust', and, in fact, trats this entire passage as something the Tao itself does rather than as something one might need to contrive based on it. Most other translators seem to agree. This said, Fengs interpretation is well worth the consideration 'politically'.
 Lau has 'Darkly visible, it only seems as if it were there.
 The ma wang tui text (echoed by most others has '... the Lord' with Henricks's note that: "Lord" (ti) was the name of the supreme deity of the Shjang people (traditionally 1766-1122 BCE) , and was also used as the name of the supreme god of the Chou (1122-221 BCE), though they more commonly used the name 'Heaven' (t'ien).
After a section where he points out that anyone trying to govern without a full understanding of the active and passive principles (yin-yang) - any 'one trick pony' government - cannot possibly serve to support them, Wang goes on to say:
Although Earth consists of physical forms with their earthbound souls, if it did not take its model from Heaven, it would not be able to keep its quietude intact. Although Heaven consists of embryonic essences with their images, if it did not take its model from the Dao, it would not be able to preserve its purity. Used as an empty vessel, the Dao's utility is inexhaustible, but if one tries to fill it and turn it into something full... itsimply overflows... (W)hat makes it inexhaustible already fills it completely.
No matter how vast a physical form, nothing hampers the Dao's power to embody. No matter how great an undertaking, nothing could utilise its entire capacity. If the myriad things thought to abandon it and seek a different master, where could such a master be found? Indeed, is not true that 'it is such an abyss, oh, that it appears to be the progenitor of the myriad things'? It blunts the sharp but suffers no damage, cuts away the tangled but is not worn out, merges with the brilliant but does not soil its power to embody, and becomes one with the very dust but does not compromise its authenticity. Indeed, is it not true that 'its depth is so deep, oh, that it merely seems to exist'?
Since Earth must keep its physical form, its virtue (teh)(*) cannot exceed what it upholds, and, since Heaven must remain content with its images, its virtue cannot exceed what it covers. Thus neither Heaven nor Earth can equal it. Indeed, is it not true that 'it appears to have been born before the Lord(ti)', meaning t'ien ti, 'the Lord of Heaven'?
(*) Perhaps Waley's version ('power') - virtue in the ancient sense of the word - capacity - would be a happier translation here.
Cheng says: In application, the Tao blends in and is therefore empty yet can never be filled. Chapter 45 says, 'The greatest fullness seems empty, yet its applications are never exhausted'. Thus the 'body' of the Tao is 'so deep, ah! that it seems to be the ancestor of all things', blunting edges and solving quandaries as if all were returning to the oneness of non-action. Glare is mitigated and the world united as deeply as if a great spirit were there. Whose child is it? 'It seems to have existed before the Ancestor', referring to chapter 25, 'there is a chaotic thing, born before heaven and earth... I do not know its name. I reluctantly style it 'Tao', and, if forced to, would reluctantly decribe it as 'great'.
The idea is simple (aha! - that word!)... The Tao acts without conscious doing, therefore it is never over-extended, never exhausted.
Anything you want to add to its workings is useless... you cannot beat a heart or grow a seed... they do this of themselves. As the Zenrin Kushu (a book of some of the standard responses to the famous Zen koans) says:
'Spring comes and - of themselves - the grasses grow,
Some short, some long.'
Ch'uang-tze asks of the mind that would meddle, 'Which will you do? Stretch the legs of all ducks, or cut off those of the cranes?' The Whole Earth Catalogue guys said concerning the planet: 'You can't get it together. It is together.'
And it acts out of the utterly impalpable.... Things seem to come into being, persist for a brief instant and then dissolve back into the emptiness, only to be replaced by other things, similar or different, instant by instant, day by day, aeon by aeon... None of it is more than a mere blink in time, a simple flash in the vastness of space, and even time/space itself is just a joke.
The source of all sources, manifest simultaneously as the vast and endless display...
In the practice of t'ai chi ch'uan, as the enactment of non-doing, all movement stems from, manifests within and then returns back into this 'emptiness' in its various guises.