I saw this on a needle-disposal box in a medical clinic.

Problem:
The verb “assure” is incorrect for this sentence.

Explanation:
The verb “assure” essentially means to set the mind at rest. Use “assure” when you want to say that you are setting someone’s mind at rest. The verb “insure” essentially means to guarantee against risk. Use “insure” when you want to say that you are protecting people or property against risk. The verb “ensure” essentially means to make sure. Use “ensure” when you want to say that you are making certain that something will happen or that something is true.

Solution:
“Lift to ensure disposal.”