Taken from the Foreign Workers Manual section dealing with LMOs on page 88 onwards
Processing temporary foreign workers—Documents required with application
The following documents are required:
1. application form;
2. cost-recovery fee, or HPM receipt (unless fee exempt, see R299 for work permit fee and exemptions)
3. evidence that the eligibility criteria of R200(1)(c) are met (examples of such evidence might include job offers or contracts, LMOs, acceptance into a youth exchange program, etc.);
4. background documents showing the qualifications and experience of the applicant for the employment, if such evidence is required to satisfy the requirements of R200(3)(a);
5. proof of identity (With the exception of citizens and permanent residents of the U.S. and residents of St. Pierre and Miquelon, work permits may not be issued for a duration longer than the validity of the passport);
6. a copy of the applicant’s current immigration document, if applying within Canada.
7. any other documention required to satisfy the officer that the requirements of the Act or Regulations are met.

Basically if you have an LMO that says you are a carpenter then you will have provided the employer with proof of such before the LMO is issued as a condition of the LMO being accepted. Because of this CBSA dont always ask for such proof as it has already been provided that you qualify however this proof can be asked for prior to the TWP being issued.

Ok I'm just thinking if I forget to pack any certificates whether I would get refused even if I had the LMO,contract etc. I suppose I just covering all scenarios as sometimes I have a memory like a sieve

Hopefully memory retention isnt a condition of the LMO being issued
Do not pack the certificates and LMO in a suitcase as these go missing.
Hand carry these documents then there will be no problems.
I cant definitively say you will be asked for them so its better to take them and have them just in case.

Yea it is much easier

Next step is PR. I think I will get all my documentation ready months before rather than faffing around at the last minute.

Thanks for your help