1. This will NEVER EXIST. A single object_id can never be equal to two different objects IDs at the same time. I think you're confusing the AND & OR operators.

It should be written:

WHERE object_id = OBJECT_ID( N'[dbo].[DF_locked]' )

OR object_id = OBJECT_ID( N'[dbo].[DF_count]' )

2. If the constraint already exists, you're assuming it has the definition you want. I've seen bugs get introduced with this approach. What if DF_Bit exists, but is applied to a different column then you're expecting?

3. As mentioned by ScottPletcher, you should really break the work into a separate statement for each constraint. It is possible that one of the constraint will exist, but not the other. Depending on how you fix your statement in my #1 above, you may end up missing a constraint, or have your statement fail when you try to create an existing constraint.

4. My preferred syntax for an exists test of this type is

IF OBJECT_ID('schema_name.object_name') IS NOT NULL DROP TABLE 'schema_name.object_name';

It is easily understood, fits nicely on a single line and is less typing.