Let's look at your sentence: "A crab’s claws a like fork and knife: one cuts the food and the other brings it into the mouth." It has a small mistake that we can fix.
The phrase "a like" should be "are like" because we are talking about what the claws are similar to. So, the correct sentence is:
"A crab’s claws are like a fork and knife: one cuts the food and the other brings it into the mouth."
This means that a crab uses its two claws like we use a fork and a knife. One claw helps cut the food, and the other claw helps bring the food to its mouth.