Regarding blankets, standard practice is that we don't attach tzitzis and we don't round off any corners.
Reddit user ShamanSTK asks:
I have a blanket on the couch with four corners which is almost used exclusively for day time use. It is not a blanket slept with and it is used solely for warmth when I don't feel like turning on the heat. Does it need tzitzis?
In the case of a wool blanket in the daytime, this link says to round one corner. What if ShamanSTK's blanket is made of cotton? Must he round one corner? Must he attach tzitzis?