The Monster Hunter series has had many elements changed in recent entries, especially with Monster Hunter Rise. The Clutch Claw and Slinger have been removed and replaced with the Wirebug mechanic. And some survival elements are gone as well, like the need to have hot and cold drinks for certain biomes. But something that remains is weapon sharpness, and knowing how to keep your weapon sharp can help get that sweet victory over the large monsters.
Weapon sharpness level is for all of the game's melee focused-weapons and is shown at all times at the top-left corner of the screen underneath the stamina bar. The bar is in the shape of a sword and has multiple colors lined up from red to green. At the start of every Monster Hunter Rise quest, that sharpness level will always be at the max, but what causes it to lower is when a player's weapon is used against a monster.
After each successful hit, that sharpness level will decrease and attacks might even start to bounce off the monsters, causing little to no damage. So, essentially, players will want to keep that bar as high as they possibly can during hunts. Otherwise, players won't do as much damage as they would like to, and that's not helpful.
In order for Monster Hunter Rise players to sharpen their weapon and get it back in the green (or blue, white, and purple for advanced weapons), they will need to use an item called a Whetstone, which is given to players in an infinite amount and is always ready to be used. If players look at the image below, they can see the icon of the Whetstone in the bottom-right corner. To find it in the item bar, simply hold the L button and then press either Y or A to scroll to the item.
And then to actually use it, press the Y button while the weapon is sheathed. This will start an animation that will last a few seconds, and if players get attacked during this animation, the Whetstone effect will be canceled and players will need to use it again. It's recommended that players use this when they're away from a monster and not right in the middle of a huge fight unless there's clearly a moment of respite.
Using the item bar is one way to use the Whetstone, but there is a much faster method that allows players to use the Whetstone even when their weapon is out. To do this, hold L to bring up the Radial Menu and then tap up on the right control stick. This menu can be customized in the menu to fit the player's needs, but the Whetstone will be there for brand-new players by default. Having weapons sharpened will make things a bit easier once players end up having to face off against Magnamalo, the game's flagship monster.
Monster Hunter Rise is now available for the Nintendo Switch and a PC port is expected in early 2022.