how do players in unreal 'use' items?

// The player wants to use something in the level.
exec function Use()
{
    ServerUse();
}

function ServerUse()
{
    local Actor A;
	local Vehicle DrivenVehicle, EntryVehicle, V;

	if ( Role < ROLE_Authority )
		return;

    if ( Level.Pauser == PlayerReplicationInfo )
    {
        SetPause(false);
        return;
    }

    if (Pawn == None || !Pawn.bCanUse)
        return;

	DrivenVehicle = Vehicle(Pawn);
	if( DrivenVehicle != None )
	{
		DrivenVehicle.KDriverLeave(false);
		return;
	}

    // Check for nearby vehicles
    ForEach Pawn.VisibleCollidingActors(class'Vehicle', V, VehicleCheckRadius)
    {
        // Found a vehicle within radius
        EntryVehicle = V.FindEntryVehicle(Pawn);
        if (EntryVehicle != None && EntryVehicle.TryToDrive(Pawn))
            return;
    }

    // Send the 'DoUse' event to each actor player is touching.
    ForEach Pawn.TouchingActors(class'Actor', A)
        A.UsedBy(Pawn);

	if ( Pawn.Base != None )
		Pawn.Base.UsedBy( Pawn );
}