Power to everything Nothing works

A bad ground or positive connection caught me one day. Car started fine, drove 10 miles to gas station filled her up and no start. car was fairly new to me so I had no tools with me. Sign on garage door said no tools to be lent out. I was begging for a 1/2 wrench and I guess he felt sorry for me. I retightened battery connections, started car and gave mechanic $10 and his wrench back. I now carry enough tools to swap motors out.