Hi so far I have this :

MissingBlocks.java

 

package rtester.missingblocks;

import net.minecraft.item.Item;
import net.minecraft.item.ItemSlab;
import rtester.missingblocks.blocks.ModBlocks;
import rtester.missingblocks.blocks.ObsidianHalfSlab;
import rtester.missingblocks.lib.Constants;
import cpw.mods.fml.common.Mod;
import cpw.mods.fml.common.event.FMLInitializationEvent;
import cpw.mods.fml.common.event.FMLPostInitializationEvent;
import cpw.mods.fml.common.event.FMLPreInitializationEvent;

@Mod(modid = Constants.MODID, name = Constants.MODNAME, version = Constants.VERSION)

public class MissingBlocks {

    @Mod.EventHandler
    public void preInit(FMLPreInitializationEvent event) {
    	
    	ModBlocks.init();

    }

    @Mod.EventHandler
    public void init(FMLInitializationEvent event) {

    }

    @Mod.EventHandler
    public void postInit(FMLPostInitializationEvent event) {
    	
    	Item.itemsList [ModBlocks.obsidianHalfSlab.blockID] = (new ItemSlab(
    			ModBlocks.obsidianHalfSlab.blockID - 256, (ObsidianHalfSlab) ModBlocks.obsidianHalfSlab,
    			(ObsidianHalfSlab) ModBlocks.obsidianDoubleSlab, false)); 
    }

}

 

 

ModBlocks.java

 

package rtester.missingblocks.blocks;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import net.minecraft.creativetab.CreativeTabs;
import rtester.missingblocks.lib.Constants;
import cpw.mods.fml.common.registry.GameRegistry;

public final class ModBlocks {

public static Block obsidianHalfSlab;
public static Block obsidianDoubleSlab;
public static Block obsidianStair;
public static Block obsidianWall;
public static Block obsidianFence;


public static void init(){

	//Slabs
	obsidianHalfSlab = new ObsidianHalfSlab(false, Material.rock).setBlockName(Constants.MODID + "_" + ObsidianHalfSlab.name).setBlockTextureName("obsidian").setCreativeTab(CreativeTabs.tabBlock);
	obsidianDoubleSlab = new ObsidianHalfSlab(true, Material.rock).setBlockName(Constants.MODID + "_" + ObsidianHalfSlab.name1).setBlockTextureName("obsidian");

	//Stairs
	obsidianStair = new ObsidianStair();

	//Walls
	obsidianWall = new ObsidianWall();

	//Fences
	obsidianFence = new ObsidianFence();


	//GameRegistry.registerBlock(this, name);
	GameRegistry.registerBlock(obsidianHalfSlab, ObsidianHalfSlab.name);
	GameRegistry.registerBlock(obsidianDoubleSlab, ObsidianHalfSlab.name1);
}
}

 

ObsidianHalfSlab

 

package rtester.missingblocks.blocks;


import net.minecraft.block.Block;
import net.minecraft.block.BlockSlab;
import net.minecraft.block.material.Material;
import rtester.missingblocks.lib.Constants;

public class ObsidianHalfSlab extends BlockSlab{

public static String name = "obsidianHalfSlab";
public static String name1 = "obsidianDoubleSlab";

public ObsidianHalfSlab(boolean isAfullBlock, Material mat){

	super(isAfullBlock, mat);

	this.setStepSound(soundTypePiston);
	this.setHardness(50.0F);
	this.setResistance(2000.0F);
	this.setHarvestLevel("pickaxe", 3);
	this.useNeighborBrightness = true;

}


@Override
public String func_150002_b(int p_150002_1_) {
	// TODO Auto-generated method stub
	return super.getUnlocalizedName();
}

}

 

 

Constants.java

 

package rtester.missingblocks.lib;

public class Constants {
    public static final String MODID = "missingblocks";
    public static final String MODNAME = "Missing Blocks";
    public static final String VERSION = "0.0.1";
}

 

 

 

I see several 1.6 example showing how to make slabs stack and they all use the Item.itemsList but I think in 1.7 they do not use ItemsList anymore because I cannot get it to resolve and it wants to use an int but I do not think blocks have id's anymore.

 

So I guess what my question is How do I change this to work in 1.7.10

 @Mod.EventHandler
    public void postInit(FMLPostInitializationEvent event) {
    	
    	Item.itemsList [ModBlocks.obsidianHalfSlab.blockID] = (new ItemSlab(
    			ModBlocks.obsidianHalfSlab.blockID - 256, (ObsidianHalfSlab) ModBlocks.obsidianHalfSlab,
    			(ObsidianHalfSlab) ModBlocks.obsidianDoubleSlab, false)); 
    }

 

This was the original example I seen

Item.itemsList[XoriteSlab.blockID] = (new ItemSlab(
XoriteSlab.blockID - 256, (BlockHalfSlab) XoriteSlab,
(BlockHalfSlab) XoriteSlabDouble, false));

I am sorry I am new to modding could you give me an example please of what you mean?