I am sorry, I wasnt clear. I was asking by a garbage bag if you are allowed to cross the strings over, and then tie one knot

ב"ה Shalom, Tying a bow over crossed strings for a garbage bag, raises a totally different issue. The issue is since you left the bow in place with intention for it to stay closed, after having it thrown into the garbage, does this now make the knot a permanent knot, or since he has no use for it once tossed in the garbage , it is not considered a permanent knot. There is a disagreement on this among the Rabbis. Some say that it is ok to leave the garbage bag tied with the bow over the crossed strings, while others are more stringent and say it is forbidden. Those who are lenient and those who are stringent are both brought in Piskei Teshuvot (פסקי תשובות אורח חיים סימן שיז אות יד 126 ) and their conclusion is tbat one may be lenient. However, if you want to avoid the disagreement, you may tie the bow only WITHOUT crossed strings underneath and this way poses no issue All the best