Budget heat shield

I have a Prusa i3 with the default and underpowered power supply, and keeping tall ABS jobs warm enough has always been a problem. So, I made up these little brackets and cut strips of cardboard to various heights to put in them. So, every 50mm or so as the Z-axis rises, I put little walls around the item being printed, outside the travel area of the print head, to help conserve heat in the immediate vicinity of the print. Just carefully place them on the print bed so that the print is fully enclosed, then come back every so often and replace them with higher walls.

My infrared thermometer tells me the bed stays 5-10°C warmer inside the area, depending on the print job, and I imagine the air temperature inside is slightly higher as well. It is not as effective as a full, heated enclosure, but it is a lot cheaper and easier to make.