Have you ever watched a bird sleeping on its perch and never falling
off? How does it manage to do this? 

The secret is the tendons of the bird's legs. They are so constructed
that when the leg is bent at the knee, the claws contract and grip like
a steel trap. The claws refuse to let go until the knees are unbent
again. The bended knee gives the bird the ability to hold on to his
perch so tightly. 

From sleeping birds we can learn the secret of holding things which are
most precious to us -- honesty, purity, thoughtfulness, honor, character.
That secret is the knee bent in prayer, seeking to get a firmer grip on
those values which make life worth living. When we hold firmly to God 
in prayer, we can rest assured he will hold tightly to us. 

See: Deut 4:29-31; Psalm 34:4-11; Psalm 105:3-5