Your test hole should show at least a four-inch thickness of clear ice like you get from your freezer. Wear a life jacket for extra warmth and safety. Be aware of various ice strengths and qualities. One area of a pond may be a foot thick while another spot of ice may only be an inch thick. Ice strength can also change.
Thick ice is rotten after rain.
Old honey-combed ice, slush ice or ice with current under it is also dangerous. New ice is almost always stronger that old ice. Wind, waterfowl and beavers can also keep areas of ice thin. Indiana law limits ice fishing holes to a diameter of twelve inches. Fishing shanties must have reflectors on each side so snowmobiles won't crash into them at dusk or during snowstorms.