Some of the best defensive physical walls are Skarmory, Mandibuzz and Gliscor.
They have very good defenses and skarmory and gliscor can set up rocks as well as get rid of them. While mandibuzz can get rid of rocks but has better special defense than the other 2.
Gliscor is perhaps more annoying due to it's ability, you can heal around 24% in 2 turns by using protect on the second turn.Gliscor does have a disadvantage when it comes to typing by having 4x weakness to ice. But it tanks a physical ice punch from most Pokemon when at full HP (not that you should stay in an ice punch if you predict one). But special hits cripple gliscor as well.
Skarmory is a steel type providing tons of resistances and only fire and electric as it's weakness, stay clear of this and you're fine.
Mandibuzz is really useful to switch into Pokemon who have set up 1 swords dance/Dragon dance etc and foul play nearly always kills them. And you can phase out other Pokemon who try to set up by whirlwinding as well. Mandibuzz has good HP and good defenses making her a good wall. It's also weakness to fairy, electric, ice and rock.
These are 3 good defensive Pokemon in OU.
Hope I helped :)