The holes are those in the belt for adjusting the circumference around one's waist according to one's comfort.
Normally, one wouldn't wear their trousers to bed and therefore also not their belt.
One's trousers may droop and potentially drag on the floor/ground without a belt.
The belt is a reliable "companion" which holds up one's trousers.
The title alludes to the function of a belt which is to hold up (or not let down) one's trousers.