The holes provide ventilation. Last year we discovered a premier raspberry patch adjacent a public boat landing. They were huge and we returned several times to pick them. The prior year, no berries were there. Not all patches bear fruit each year, so be sure to check your favorite haunts several times a season.
Blackberries are most plentiful in our area.
The bushes are about four to five feet high, which makes for comfortable picking, and they are easy to find. The berries are generally largest and juiciest early in the morning. We have picked several gallons of blackberries in just a few hours. I had to laugh when my son arrived home shortly after we returned from a berry-picking outing and was greeted by mounds of blackberries covering the counter tops. Carry a small can filled with a few pebbles.