EZEKIEL 1:7
 

Their legs were straight, and the soles of their feet were like the soles of calves’ feet. They sparkled like the color of burnished bronze. [Ezekiel 1:7 NKJV]
 

And their legs were straight legs, and the sole of their feet was like the sole of a calf's foot, and they sparkled like burnished bronze. [Ezekiel 1:7 AMPC]

Behold the legs and feet of the Rabim: 
 

The shape of their legs was straight, without leg curves, to avoid any part of their legs favoring any direction over the the direction or to avoid their legs revealing their front-side, back-side, left or right sides. This is unlike the legs of a man that have shapes, curves and features, that face/favor some sides of the man over the other sides of man, and betray either his front side, back side, right side and left side. There was no way for one to decide any direction or side view of those living creatures just by beholding their legs.
 

Also, the soles of their feet were not like the soles of man's feet, but like the soles of Calf's feet/hoofs. Man has feet that project forward in the direction of the man's frontwards. You can tell which direction of a man's sides is his front side or forward, backside, left or right sides, just by beholding the man's feet, sole of his feet or even footprints. But you cannot use the footprints of these Living Creatures, the Rabim, to determine their direction, neither can you tell their sides' views just by studying the soles of their Feet.
 

Aggregatedly, their four faces, their four wings, their straight legs, their calf-like feet, make their direction, their front/forward, their movement or their next steps, too mysterious to predict by human senses. They simply have no navigation indicators or pointers both as they stand and as they move.
 

But why is it important for the four Living Creatures to be without directional navigator or direction indicator?
 

The reason includes those Four Living Creatures were escorts who travel with God, and therefore they must not be leaving clues as to where God is coming from or where He's going. They must be as the wind which navigation and direction cannot be predictable. As it is written,
 

[John 3:8] — "The wind blows where it wants, and you hear the sound thereof, but can not tell from where it comes, and where it goes: so is every one that is born of the Spirit."
 

Imagine a King or President who moves with escorts that pre-announces the next moves, directions or next steps/stops of their Leader. Wouldn't it be easier for men to fathom the King or President, and even anticipate His next moves/steps before He makes them?

Another thing to behold at their legs and feet was the appearance of Bronze/Brass that toned the complexion and countenance of their legs and feet. This reflected both strength and wealth. Thus, their legs and feet that were like calf's feet were indeed rich treasures and were pillars of strength, able to abide the furnace fire and stressful weights. That accounted for the colors of Amber or Embers of Amber, which are related to the colors of burnished Bronze or polished Brass.