Warning: the Tuesday my kid flushed a matchbox car and I found out our shutoff valve was painted shut
Standing in 2 inches of water in our only bathroom on a Tuesday night and the valve behind the toilet would not turn because somebody painted over it years ago. Ran to the basement, found the main shutoff, and it took both hands and a wrench to crank it closed while my kid yelled that the water was still going. Plumber quoted $340 just to swap the valve and said he sees this in half the houses he visits. Now I check every valve in the house once a month and keep a wrench taped inside the basement door. If your shutoff has not moved in years, go test it tonight before you are the one standing in a puddle.