This is Heath's Lead guitar parts in their official 'Hold On' video:
http://www.youtube.com/watch?v=Le-3MIBxQTw

Standard tuning.

Start (Palm mute)

E|-----X--------X--------X-----------------|
B|-----X--------X--------X-----------------|
G|-----X--------X--------X-----------------|
D|-----X--------X--------X-----------------| X2
A|--3--X--3--3--X--3--3--X----3----3-------|
E|--3--X--3--3--X--3--3--X--5----5---5--5--|

Verse 1, 2, 3.

E|-------------------------------------|
B|-------------------------------------|
G|-------------------------------------|
D|-------------------------------------|
A|-----7-----3-----------3-----3-------|
E|--5-----5-----5--3--5-----5-----5----|

Chorus 1, 2, 3.

First part

E|------------------------------------------------------------------------------|
B|------------------------------------------------------------------------------|
G|------------------------------------------------------------------------------|
D|---------10---------10----------------10---------10----------------10---------|
A|--10h12------10h12------10h12--10h12------10h12------10h12--10h12------10h12--|
E|------------------------------------------------------------------------------|


E|--------------|
B|--------------|
G|--10--10/12---|
D|--12--12/14---|
A|--------------|
E|--------------|

Second part

E|------------------------------------------------------------------------------|
B|------------------------------------------------------------------------------|
G|------------------------------------------------------------------------------|
D|---------10---------10----------------10---------10----------------10---------|
A|--10h12------10h12------10h12--10h12------10h12------10h12--10h12------10h12--|
E|------------------------------------------------------------------------------|


E|--------------|
B|--------------|
G|--10/12--10---|
D|--12/14--12---|
A|--------------|
E|--------------|

Third part

E|------------------------------------------------------------------------------|
B|------------------------------------------------------------------------------|
G|------------------------------------------------------------------------------|
D|---------10---------10----------------10---------10----------------10---------|
A|--10h12------10h12------10h12--10h12------10h12------10h12--10h12------10h12--|
E|------------------------------------------------------------------------------|

E|--------------|
B|--------------|
G|--10--10/12---|
D|--12--12/14---|
A|--------------|
E|--------------|

Fourth Part

(b>): Bend up (b<): bend down

e|-----------------------------------------------------|
B|------------------------------------13-13-13---------|
G|--------12-------------------10/12--14-14-14--12/----|
D|---12(b>)------12(b<)---10---12/14------------14/----|
A|-----------------------------------------------------|
E|-----------------------------------------------------|

In chorus 2 & 3 Heath joins Brittany on the Chords but with a few minor alterations.

E|--0--|
B|--1--|
G|--0--|
D|--2--|
A|--3--|
E|--3--|

E|------|
B|------|
G|--14--|
D|--14--|
A|--12--|
E|------|

Ending (Palm mute)

E|--------------------------------------------------|
B|--------------------------------------------------|
G|--------------------------------------------------|
D|--------------------------------------------------|
A|-----7-----3-----------3-----3-----7--5--3--------|
E|--5-----5-----5--3--5-----5-----5-----------5--3--|

E|-----------------------|
B|-----------------------|
G|-----------------------|
D|-------------3--(b)12--|
A|-----------3-----------|
E|--3--(h)5--------------|

Heath also slides the lower E string down from the 15th threat with the bassist on the
second part of chorus 2 & 3.