Method tryPlace

src/main/java/net/minecraft/item/ItemSlab.java:111–134

(ItemStack stack, World worldIn, BlockPos pos, Object variantInStack)

    }

    private boolean tryPlace(ItemStack stack, World worldIn, BlockPos pos, Object variantInStack)
    {
        IBlockState iblockstate = worldIn.getBlockState(pos);

        if (iblockstate.getBlock() == this.singleSlab)
        {
            Comparable comparable = iblockstate.getValue(this.singleSlab.getVariantProperty());

            if (comparable == variantInStack)
            {
                IBlockState iblockstate1 = this.doubleSlab.getDefaultState().withProperty((IProperty)this.singleSlab.getVariantProperty(), comparable);

                if (worldIn.checkNoEntityCollision(this.doubleSlab.getCollisionBoundingBox(worldIn, pos, iblockstate1)) && worldIn.setBlockState(pos, iblockstate1, 3))
                {
                    worldIn.playSoundEffect((float)pos.getX() + 0.5F, (float)pos.getY() + 0.5F, (float)pos.getZ() + 0.5F, this.doubleSlab.stepSound.getPlaceSound(), (this.doubleSlab.stepSound.getVolume() + 1.0F) / 2.0F, this.doubleSlab.stepSound.getFrequency() * 0.8F);
                    --stack.stackSize;
                }

                return true;
            }
        }

        return false;
    }
}