When trained on walls and fences these deciduous and evergreen shrubs are kept growing flat against those by cutting back shoots to within two to four buds of the framework of permanent branches. This is best done in late-spring because then you won't loose the buds you selected due to frost damage or die-back.
Before the shrub now starts growing again it is useful to check that the wall or fence is in good condition: You've got to provide a sturdy means of attachment for the plant since the older it gets the more difficult it can be to detach. Moreover, check all ties and replace any that are broken or (close to) cutting into the stems. Watch your wall-shrub and how its framework thickens year by year to help you decide on the appropriate ties: Some material is more expandable than others e.g. cotton but can rot away quicker. With rubber tube ties you may find that in direct sun they soon lose their flexibility and become brittle.