The 49ers hosted Seahawks restricted free agent offensive tackle Garry Gilliam for a visit today, a source tells Field Yates of ESPN.com (on Twitter). Seattle tendered him at the original round level. Because Gilliam was undrafted, Seattle will not be entitled to any draft compensation if he is signed away. 
Gilliam, 26, appeared in 14 games for the Seahawks last season and made 13 starts. Unfortunately, his performance left much to be desired as the entire Seahawks offensive line sagged. Gilliam finished out the year with an abysmal 38.0 overall score on Pro Football Focus, framing him as one of the ten worst qualified tackles in the NFL. The Seahawks wound up using him on 939 snaps, which would explain much of their O-Line woes. Fellow Seattle tackle George Fant, who was on the field for 792 snaps, had the worst grade of any tackle in the league at 27.6.
The Seahawks probably do not intend on using Gilliam as a starter again in 2017, but they would like to have him back as a reserve. The Niners, meanwhile, are likely kicking the tires on him as a depth signing. There will be cheaper and younger options in the draft, so the Seahawks would have to be pretty fond of him to sign him to an offer sheet.