diff --git a/README.md b/README.md
index 91abdb7..a080d8b 100644
--- a/README.md
+++ b/README.md
@@ -59,13 +59,33 @@ This works with the `--post-mortem` flag, so -- provided docker is installed --
 you can even use `TryCI` to prod around in a CI job on machines which you
 haven't cloned the original repo or setup to develop on.
 
+## Using bindmounts for faster build times
+
+Sometimes a CI build will depend on a submodule or external program which the
+`.buildbot.sh` script builds from source each time. For large projects (like
+`ykllvm`, which can take up to an hour to build) this can make build times
+significantly slower.
+
+Instead, you can mount arbitrarily many prebuilt programs from the host to be
+used inside the docker container using `-m/--mount` flag. You can specify
+multiple bind-mounts by repeating the option or by providing a comma-separated
+list:
+
+```
+-m /src:/dst -m /foo:/bar:ro
+-m /src:/dst,/foo:/bar:ro
+```
+If using this with the `--remote` flag, you must ensure the directory you wish
+to bind-mount exists on the remote machine -- it does not `scp` / `rsync` it
+over.
+
 ## Troubleshooting
 
 * Docker must be installed on both the local machine and remote machine used to
   compile and run the build.
 * Your user account on both the local and remote machine must be a member of the
   `docker` group.
-* If running CI on a remote machine (`--remote server_name`) you must use ssh
+* If running CI on a remote machine (`--remote <server_name>`) you must use ssh
   passwordless login (using public/private key pair).
 
 
diff --git a/tryci b/tryci
index 061cbef..9f061ff 100755
--- a/tryci
+++ b/tryci
@@ -31,19 +31,12 @@ usage() {
 Runs a soft-dev CI job.
 Must be run from the same directory as the job's .buildbot.sh file.
 
-usage: tryci [-p] [-r server_name] [-b <ref>] [-h]
+usage: tryci [-h] [-c <ref>] [-m <mount>...] [-p] [-r <server-name>]
 
 Options:
-  -p, --post-mortem
-      Attach a shell to the image to prod around if the build fails.
-
-  -r, --remote server_name
-      Specify the server \`server_name\` to run the CI job on over SSH.
-      Useful if you want to test on a remote CI environment.
-
   -c, --checkout <ref>
-      Tryci will run a CI job from a clone of <ref> instead of the
-      working tree. Valid formats:
+      Run a CI job from a clone of <ref> instead of the working tree. Valid
+      formats:
       - Branch name (e.g., main, feature/x)
       - Commit hash (e.g., a1b2c3d)
       - Tag (e.g., v1.0.0)
@@ -51,6 +44,21 @@ Options:
       - Remote URL with branch (e.g., https://github.com/user/repo#branch)
       Useful for debugging the exact version of a CI job that failed on CI.
 
+  -m, --mount <mount> [<mount> ...]
+      Specify one or more bind-mounts. Each <mount> should be in the form:
+        <host-path>:<container-path>[:ro|rw]
+      You can specify multiple bind-mounts by repeating the option or by
+      providing a comma-separated list:
+        -m /src:/dst -m /foo:/bar:ro
+        -m /src:/dst,/foo:/bar:ro
+
+  -p, --post-mortem
+      Attach a shell to the image to prod around if the build fails.
+
+  -r, --remote <server-name>
+      Specify the server <server-name> to run the CI job on over SSH.
+      Useful if you want to test on a remote CI environment.
+
   -h, --help
       Show this help message and exit.
 EOF
@@ -182,7 +190,7 @@ build_image() {
     container_tag=$(docker create \
       ${CAP_ARGS} \
       -u "${ci_uid}" \
-      -v /opt/ykllvm_cache:/opt/ykllvm_cache:ro \
+      ${volumes}
       "${image_tag}")
 }
 
@@ -214,6 +222,7 @@ run_image() {
 pm=0
 server=""
 ref=""
+volumes="-v /opt/ykllvm_cache:/opt/ykllvm_cache:ro"
 
 while [ $# -gt 0 ]; do
   case $1 in
@@ -229,6 +238,25 @@ while [ $# -gt 0 ]; do
       ref="$2"
       shift 2
       ;;
+    -m | --mounts)
+      # Support both repeated and comma-separated mounts
+      shift
+      if [[ -z "$1" || "$1" =~ ^- ]]; then
+        error "--mounts requires an argument."
+        exit 1
+      fi
+
+      IFS=',' read -ra mounts <<< "$1"
+      for m in "${mounts[@]}"; do
+        if [[ ! "$m" =~ ^[^:]+:[^:]+(:ro|:rw)?$ ]]; then
+          error "Invalid bind mount: '$m'"
+          error "Expected format: /host/path:/container/path[:ro|rw]"
+          exit 1
+        fi
+        volumes+=" -v $m"
+      done
+      shift
+      ;;
     -h | --help)
       usage
       exit 0