A cold frame can be anything from a clear sweater box or other clear container to a consumer product such as a juwel coldframe. You can construct the sides out of most anything, bales of straw, bricks, lumber and then place some repurposed glass like out of a storm door over the surface.
After the night time lows hit 45 degrees or warmer and the day time highs are 65 or warmer, I leave my plants outside both day and night. At first they are enclosed in two Juwel cold frames, but after they outgrow the cold frame, they continue to stay outside, until planted in the garden.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.