In Minecraft speedrunning, players often split their items into halves as part of a technique called "item duplication." Item duplication allows them to quickly acquire more valuable resources and items, which can significantly speed up the process of completing the game. Here's how it works:

1. Basic Duplication: To duplicate items, a player will place a set of items into a crafting table. They split the items into two equal stacks, leaving one item behind in the crafting grid. Then, they take the resulting duplicate stack, effectively doubling their items.
2. Resource Efficiency: This technique is commonly used for items that are hard to obtain or are resource-intensive to create. By duplicating valuable resources, players can save time and effort, making it easier to achieve their speedrun goals.
3. Speedrunning: In speedrunning, the goal is to complete the game as quickly as possible. Item duplication can help speed up various aspects of the game, such as acquiring rare items, gathering resources for building and crafting, or even duplicating key resources needed for game progression.
4. Glitches and Techniques: Item duplication is often possible due to glitches or unintended mechanics in the game. Speedrunners exploit these glitches to their advantage, enabling them to save time and streamline their progress through the game.
5. Controversy: The use of item duplication techniques in Minecraft speedrunning is a subject of controversy. Some purists believe that it undermines the challenge of a speedrun, while others argue that it's a legitimate strategy as long as it adheres to the rules and categories established by the speedrunning community.

It's important to note that the acceptability of item duplication in Minecraft speedrunning may vary depending on the specific speedrun category, rules, and the preferences of the community hosting the event or tracking the records. If you're interested in speedrunning Minecraft, it's essential to familiarize yourself with the specific rules and guidelines of the community you're participating in.