bamboo tape (for basketwork); bamboo slat (of a paper fan)

miserably hard; difficult; tough

difficult to solve

(vehicles) a spoke (part of a wheel)

(of disease) difficult to cure

(literally) it's difficult either to advance or to retreat

getting started is the hardest part

(literally) fire tests gold, hardship tests strength / (figurative) only hardship can test your ability and endurance; to be better, you need to put yourself through hardship

a word once spoken cannot be taken back; a promise must be kept; a promise is a promise