To make a tripwire on Minecraft you need a piece of string, two tripwire hooks and two solid blocks. Suspend the tripwire across a space by fixing either end of a piece of string to a tripwire hook. Attach each tripwire hook to one of the solid blocks.
Obtain tripwire hooks and string by fishing, or find them in jungle temples. Spiders and cave spiders can drop string when they die. Alternatively, craft tripwire hooks using wood planks, an iron ingot and a stick.
Use tripwires in redstone circuits as a trap for players or mobs. Cut through tripwires with shears, or use tools to remove them.