A telescopic weld? That is a term new to me. Often signage uses joints that are telescopic in configuration such as sleeved tubing or pipe. The interior member may be fillet welded or plug/slot welded to maintain positioning (elevation/extension) of the sleeved-tubular joint. The joint is moved in/out until the required/desired dimensional value is achieved.
This is often specified for the benefit of the erection crew to accomodate for conditions encountered in the field.
